Category: Class 9

AP State Syllabus AP Board 9th Class Physical Science Solutions Chapter 8 Gravitation Textbook Questions and Answers.

AP State Syllabus 9th Class Physical Science Solutions 8th Lesson Gravitation

9th Class Physical Science 8th Lesson Gravitation Textbook Questions and Answers

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Question 1.
What path will the moon take when the gravitational interaction between the moon and earth disappears? (AS 2)
Answer:
The force of attraction between moon and earth is given by F = \(\frac{\mathrm{GMm}}{\mathrm{R}^{2}}\)
M = mass of the earth ; m = mass of the moon ; R = radius of the earth
Here the gravitational interaction between moon and earth disappears.
∴ G = 0 ⇒ F = 0

• Therefore the moon neither revolves around the earth nor fall into the earth.
• It takes a straight path away from the earth.

Question 2.
A Car moves with constant speed of 10 m/s in a circular path of radius 10 m. The mass of the car is 1000kg. Who or what is providing the required centripetal force for the car? How much is it? (AS 1)
Answer:
Speed of the car (v) = 10 m/s ; Radius of the path (r) = 10 m
Weight of the car (m) = 1000kg

The required centripetal force is provided by the friction between the tyres of the car and the road.

Question 3.
A small metal washer is placed on the top of a hemisphere of radius R. What minimum horizontal velocity should be imparted to the washer to detach it from the hemisphere at the initial point of motion? (AS 1, AS 7)

Answer:
Radius of hemisphere = R; Mass of hemisphere = M
Let the radius of washer = r and mass = m
Distance between hemisphere and washer = R + r
The centripetal force required to rotate the washer = \(\frac{\mathrm{mv}^{2}}{\mathrm{r}}\)
The gravitational force of washer due to hemisphere is = \(\frac{\mathrm{GMm}}{\mathrm{R}^{2}}\)
But the necessary centripetal force must be equal to the gravitational force

Question 4.
Explain why a long pole is more beneficial to the tight rope walker if the pole has slight bending. (AS 1, AS 7)
Answer:

• You must have noticed the circus artists doing rope walking.
• During this act, they carry a long bamboo pole in their hands.
• The reason for this is that the line joining the centre of gravity and centre of equilibrium must fall within the rope for achieving the stable equilibrium.
• Thus when an artist finds that he is falling towards left, he shifts bamboo pole towards right, so that his centre of gravity stay undisturbed.
• Thus he can balance himself on the rope.

Question 5.
Why is it easier to carry the same amount of water in two buckets, one in each hand rather than in a single bucket? (AS 7)
Answer:
It is because in the later case centre of gravity of our body shifts towards the bucket and there is a tendency that the line joining the centre of gravity and centre of equilibrium may fall outside our feet.

However in the former case the centre of gravity not only gets lowered, but also it is at such a point that line joining the C.G. and C.E. falls within our feet.
Hence one is a stable equilibrium.

Question 6.
What is the speed of an apple dropped from a tree after 1.5 second? What distance will it cover during this time? Take g = 10 m/s². (AS 1)
Answer:
An apple is dropped from a tree.
∴ Initial velocity u = 0 ; Time t = 1.5 s
a = g = 10 m/s2 ; Final velocity v = ?
v = u + at = 0 + 10 x 1.5 = 0 + 15 = 15 m/s
Distance covered (s) = ut + \(\frac{1}{2}\) at² = 0 × 1.5 + \(\frac{1}{2}\) × 10 × 1.5 × 1.5 = 0 + 5 × 2.25 = 11.25 m

Question 7.
A body is projected with a speed of 40 m/s vertically up from the ground. What is the maximum height reached by the body? What is the entrie time of motion? What is the velocity at 5 seconds after the projection? Take g = 10 m/s². (AS 1)
Answer:
Initial speed u = 40 m/s ; g = 10 m/s²
Maximum height reached (h) = \(\frac{\mathrm{u}^{2}}{2 \mathrm{~g}}=\frac{40 \times 40}{2 \times 10}\) = 80 m
Entire time of motion (T) = \(\frac{2 \mathrm{u}}{\mathrm{g}}=\frac{2 \times 40}{10}\) = 8 s
Entire time of motion is 8 seconds.
∴ It starts to fall down after 4 seconds.
At 5 seconds the body is in downward direction.
u = 0 m/s, a = g = 10 m/s², t = 5 – 4 = 1 sec.
v = u + at = 0 + 10 × 1 = 10 m/s
∴ The velocity at 5 seconds is 10 m/s downward.

Question 8.
A boy is throwing balls into the air one by one in such a way that when the first ball thrown reaches maximum height he starts to throw the second ball. He repeats this activity. To what height do the balls rise if he throws twice in a second? (AS 1, AS 7)
Answer:
The boy throws the second ball when the first ball reaches its maximum height. He throws twice in a second.
Time of ascent of first ball is 1/2 sec.
After 1/2 sec, the first ball starts to fall down and the second ball starts from ground.
Let the distance travelled = s meters.; Initial velocity = u m/s
Time of ascent (t₁) = 1/2 sec.

They reach a height of 15/4 meters.

Question 9.
A man is standing against a wall such that his right shoulder and right leg are in contact with the surface of the wall along his height. Can he raise his left leg at this position without moving his body away from the wall? Why? Explain. (AS 7)
Answer:

• When the right leg and right shoulder are in contact with the surface of the wall along the height of a man, his weight is towards the wall.
• The centre of gravity will be away from the foot. Just like in the case of carrying a bucket full of water with one hand.
• The line joins the centre of gravity and centre of equilibrium is not perpendicular to the horizontal.
• Hence he cannot lift his left leg without moving his body along the wall.

Question 10.
A ball is dropped from a height. If it takes 0.2 s to cross the last 6 m before hitting the ground, find the height from which it is dropped. Take g = 10 m/ s². (AS 1)
Answer:

For last 6 m, distance travelled
s = 6 m ; u = ? ; t = 0.2 sec ; a = g = 10 m/s²
s = ut + \(\frac{1}{2}\) at²
6 = u (0.2) + \(\frac{1}{2}\) × 10 × (0.2)²
6 = (0.2) u + (5 × 0.04)
6 – 0.2 = 0.2 u
5.8 = 0.2 u ⇒ u = \(\frac{5.8}{0.2}\) = 29
∴ u = 29 m/s
This u will be the final velocity while travelling the distance x.
∴ s = x, v = 29 m/s, a = g = 10 m/s², u = 0 m/s
v² – u² = 2as ⇒ 29² – 0 = 2 × 10 × x ⇒ x = \(\frac{841}{20}\) = 42.05 m
∴ Total distance = x + 6 = 42.05 + 6 = 48.05 m
∴ The ball is dropped from a height of 48.05 m.

Question 11.
A ball is dropped from a balloon going up at a speed of 5 m/s. If the balloon was at a height 60 m. At the time of dropping the ball, how long will the ball take to reach the ground? (AS 1, AS 7)
Answer:
At t = 0, the stone was going up with a velocity of 5 m/s. After that it moves as a freely falling body, with downward acceleration ‘g’.
If it reaches the ground at time t₁,

Question 12.
A ball is projected vertically up with a speed of 50 m/s. Find the maximum height, the time to reach the maximum height, and the speed at of the maximum height. (g = 10 m/ s²) (AS 1)
Answer:
Initial speed u = 50 m/s ; g = 10 m/s²

After reaching maximum height, the velocity becomes ‘zero’.

Question 13.
Two cars having masses m₁ and m₂ move in circles of radii r₁ and r₂ respectively. If they complete the circle in equal time. What is the ratio of their speeds and centripetal accelerations? (AS 1)
Answer:
Masses of cars : m₁ and m₂; Radius of circles : r₁ and r₂
Given that their time period is equal.

Question 14.
Two spherical balls of mass 10 kg each are placed with their centers 10 cm apart. Find the gravitational force of attraction between them. (AS 1)
Answer:
Masses of balls M₁ and M₂ = 10 kg each.; Distance d = 10 cm = 0.1 m
Gravitational force of attraction between them is

Question 15.
Find the free-fall acceleration of an object on the surface of the moon, if the radius of the moon and its mass are 1740 km and 7.4 × 10²² kg respectively. Compare this value with free fall acceleration of a body on the surface of the earth. (AS 1)
Answer:
Radius of the moon = 1740 km = 1740 × 10³ m
Mass of the moon = 7.4 × 10²² kg ; G = 6.67 × 10^-11 Nm² kg^-2
Free fall acceleration of a body on the surface of the moon

Question 16.
Can you think of two particles which do not exert gravitational force on each other? (AS 2)
Answer:
Two particles which do not exert gravitational force on each other will be mass less particles. But every particle has even a little mass. Hence we cannot find two particles which do not exert gravitational force on each other.

Question 17.
An apple falls from a tree. An insect in the apple finds that the earth is falling towards it with an acceleration g. Who exerts the force needed to accelerate the earth with this acceleration? (AS 7)
Answer:

• According to Newton’s third law, when an apple is freely falling, the force on the apple due to earth is equal to the force on the earth due to apple.
• The force is due to gravity, which causes acceleration in the body.
• As the insect is inside the freely falling apple, it feels that the earth is falling towards it with an acceleration ’g’.
• According to the insect, the acceleration is due to the force on the apple due to the earth.
• Actually the earth is not falling towards the apple.

Question 18.
A scooter weighing 150 kg together with its rider moving at 36 kin/hr is to take a turn of radius 30 in. What force on the scooter towards the center is needed to make the turn possible ? Who or what provides this? (AS 1)
Answer:
Weight of the scooter with rider = 150 kg
Speed = 36 km/hr = 36 × \(\frac{5}{18}\) = 10 m/sec.
Radius of the turning = 30 m
The force needed on the scooter towards the centre is centripetal force.

∴ A centripetal force of 500 N is required on the car.
This force is provided by the friction between the tyres of the car and road.

Question 19.
The bob of simple pendulum of length 1 m has mass 100 g and a speed of 1.4 m/s at the lowest point in its path. Find the tension in the string at this moment. (Take g = 9.8 m/sec²) (AS 1)
Answer:
Mass of the bob = 100 g = 0.1 kg ; Length of the string = 1 m
Speed of the bob v = 1.4 m/s ; Let the tension in the string be T.
The forces acting on the bob are

a) Weight of the bob mg, downwards
b) Tension in the string ‘T’ upward
Weight of bob = \(\frac{\mathrm{mv}^{2}}{\mathrm{l}}\)
Tension in the string T = g cos θ
∴ According to Newton’s third law

Question 20.
How can you find the centre of gravity of India map made with steel? Explain. (AS 3)
(OR)
Describe an activity to know the center of gravity of a India map.
Answer:

1. Take an India map made of steel.
2. Make holes at four different corners i.e., top, bottom, left, and right, and name them as A, B, C, and D as shown in figure.
3. Suspend the map through a hole A, by means of a string to a nail ‘P’ as shown in figure.
4. Suspend a plumb line from the nail P.
5. Draw the line AX along the plumb line.
6. Similarly suspend the map through other holes B, C and D and draw lines BY, CZ, DW along the plumb line.
7. These lines (more than two) intersect at a point.
8. This point (G) is the centre of gravity of the map.

Question 21.
Explain some situations where the center of gravity of man lies out side of the body. (AS 1)
Answer:
Centre of gravity of a human being is located interior to the second sacral vertebra.
Centre of gravity of man lies out side the body in the following situation :
a) While doing sit-ups.
b) While carrying a load like bucket full of water with one hand.
c) While walking on a narrow base like walking on a rope or pole or narrow wall, etc.
d) While walking with one leg.
e) As age increases its position changes.

Question 22.
Where does the centre of gravity of atmosphere of the earth lie? (AS 2)
Answer:
The earth’s atmosphere is about 10,000 km thick, but most of its bulk is contained in the first 11 km above the earth’s surface. Since the earth and its atmosphere are roughly spherical, the centre of the earth is also the centre of gravity of the earth’s atmosphere.

Question 23.
Where does the center of gravity lie, when a boy is doing sit-ups? Explain. (AS 7)
Answer:

• The centre of gravity of a boy when he start erect, falls in the foot.
• When he is doing sit-ups, the centre of gravity shifts from foot to his base.
• The weight vector also move from the base.
• Hence the boy stretches his hands or bends slightly towards the earth. While doing sit-ups, in order to make the weight vector pass through base, so that he acquire stability.

9th Class Physical Science 8th Lesson Gravitation InText Questions and Answers

9th Class Physical Science Textbook Page No. 126

Question 1.
What is that force?
Answer:
The force acting on these objects to make them move around another object, instead of moving in straight line in the gravitational force.

Question 2.
Is the motion of the earth around the sun uniform motion?
Answer:
The earth takes 365.25 days to complete one rotation around the sun. Hence it is uniform motion.

Question 3.
Is the motion of the moon around the earth uniform motion?
Answer:
Moon takes 27.3 days to complete one rotation around the earth, which does not change. Hence it is uniform motion.

9th Class Physical Science Textbook Page No. 127

Question 4.
Does the velocity of the body change in uniform circular motion? Why?
Answer:
The velocity of the body in uniform circular motion is constant.

If the velocity is not constant, the time period changes from time to time and it cannot be treated as uniform circular motion.

Question 5.
Does the body in uniform circular motion have an acceleration? What is the direction of acceleration?
Answer:
The body in uniform circular motion have an acceleration, which is directed towards the centre of the circle, known as centripetal acceleration.

9th Class Physical Science Textbook Page No. 129

Question 6.
Do you know what questions arose in his mind from this observation?
Answer:
When apple fell to the ground, Newton might have thought like this:
a) Why did the apple fall on the earth?
b) Why doesn’t the apple go up in the sky?
c) Whether all the objects fall to ground ?
d) What makes them to fall on the ground?

Question 7.
Why did the apple fall to the ground?
Answer:
The apple fell to the ground due to the gravitational attraction of the earth.

Question 8.
Why does the moon not fall to the ground?
Answer:
The gravitational force in the moon due to earth is equal to the gravitational force on the earth due to moon. Hence the moon does not fall to the ground.

Question 9.
What makes the moon to move in a circular orbit around the earth?
Answer:
The gravitational force between moon and earth act as centripetal force and makes the moon to revolve around the earth in uniform circular motion.

9th Class Physical Science Textbook Page No. 135

Question 10.
How do you feel during the free-fall of your body from the height?
Answer:

• I feel weightlessness during the free-fall of my body from the height.
• This is due to the gravitational force of earth on the body.

9th Class Physical Science Textbook Page No. 136

Question 11.
Try to balance ladder on your shoulder. When does it happen?
Answer:
When the centre of gravity of the ladder and the centre of gravity of our body lies in the same line then we can balance the ladder on our shoulders.

9th Class Physical Science Textbook Page No. 128

Question 12.
Can an object moVe along a curved path if no force acts on it?
Answer:

• If a body has to move in a curved path, its direction of velocity must change continuously.
• This is done by the centripetal force.
• Hence an object cannot move along a curved path if no force acts on it.

Question 13.
As a car speeds up when rounding a curve, does its centripetal acceleration increase? Use an equation to defend your answer.
Answer:
Centripetal acceleration \(a_{c}=\frac{v^{2}}{r}\)
As v increases, its centripetal acceleration also increases.

Question 14.
Calculate the tension in a string that whirls a 2 kg – toy in a horizontal circle of radius 2.5 iv when it moves at 3 m/s.
Answer:
Mass of the toy m = 2 kg ; Radius of the circle = 2.5 m ; Speed of the toy = 3 m/s
As the toy is moving in a horizontal circle, the necessary centripetal force is provided due to the tension in the string.

9th Class Physical Science Textbook Page No. 131

Question 15.
In figure, we see that the moon falls around earth rather than straight into it. If the magnitude of velocity were zero, how would it move?

Answer:
If the magnitude of velocity were zero, the moon would move towards earth due to acceleration due to gravity.

Question 16.
According to the equation for gravitational force, what happens to the force between two bodies if the mass of one of the bodies doubled?
Answer:

∴ The gravitational force will be doubled.

Question 17.
If there is an attractive force between all objects, why we do not feel ourselves gravitating toward massive buildings in our vicinity?
Answer:

• Earth is massive than the building.
• Hence the gravitational force between ourselves and earth is more than that of between ourselves and building.
• Hence we do not feel gravitating towards massive building in our vicinity.

Question 187.
Is the force of gravity stronger on a piece of iron than on a piece of wood if both have the same mass?
Answer:
Yes. The force of gravity is stronger on a piece of iron then on a piece of wood if both have the same mass.

Question 19.
An apple falls because of the gravitational attraction of the earth. What is the gravitational attraction of apple on the earth?
Answer:

• We know that acceleration due to gravity, g = \(\frac{\mathrm{GM}}{\mathrm{R}^{2}}\)
  Here M is the mass of the earth.
• In this mass of the object which is freely falling has no effect on ‘g’.
• Hence the gravitational attraction of apple on the earth is negligible.

9th Class Physical Science Textbook Page No. 133

Question 20.
Give an example for the motion of an object of zero speed and with non-zero acceleration?
Answer:
Protons and neutrons inside the nucleus.

Question 21.
Two stones are thrown into air with speeds 20 m/s, 40 m/s respectively. What accelerations are possessed by the objects?
Answer:
Stone -1 :
Initial velocity u = 20 m/s
After a time t, it reaches to ground then final velocity v = 0 m/s
Accelerahon = \(\frac{0-20}{t}=\frac{-20}{t} \mathrm{~m} / \mathrm{s}^{2}\)

Stone – 2 :
Initial velocity u = 40 m/s
Final velocity v = 0 m/s
Accelerahon = \(\frac{0-40}{t}=\frac{-40}{t} \mathrm{~m} / \mathrm{s}^{2}\)

9th Class Physical Science Textbook Page No. 135

Question 22.
When is your weight equal to mg?
Answer:
When we are on the surface of the earth, our weight is equal to ‘mg’ on earth.

Question 23.
Give example of when your weight is zero?
Answer:

1. When we are at the centre of the earth, our weight is zero.
2. When we are freely falling, we feel weightlessness.

9th Class Physical Science Textbook Page No. 138

Question 24.
Where does the centre of gravity of a sphere and triangular lamina lie?
Answer:
1) Centre of gravity of a sphere is a point where the whole mass of the sphere is assumed to be concentrated which is called centre.

2) Centre of gravity of a triangular lamina lies where the whole mass of the triangle is assumed to be concentrated which is centroid.

Question 25.
Can an object have more than one centre of gravity?
Answer:
Basing on the position or distribution of mass, an object can have more than one centre of gravity.

Question 26.
Why doesn’t the leaning tower of Pisa topple over?
Answer:

• The centre of gravity of the leaning tower of Pisa is very close to earth.
• Even though it is leaning, the line of action of total weight passes through the base. The base area of leaning tower of Pisa is very large. So it doesn’t topple over.

Question 27.
Why must you bend forward when carrying a heavy load on your back?
Answer:
If we bend forward, then the line of action of total weight passes through the body. So we are stable. Hence we must bend forward when carrying a heavy load on our back.

9th Class Physical Science 8th Lesson Gravitation Activities

Activity – 1 Uniform circular motion

Question 1.
Describe an activity to observe uniform circular motion.
Answer:
Uniform Circular Motion :
Uniform circular motion is a motion of the body with a constant speed in circular path.

Material required :
Electric motor, old C.D., small wooden block, battery, connecting chords, stop clock.

Procedure:

1. Take an electric motor and fix a disc to the shaft of the electric motor.
2. Place a small wooden block on the disc, as shown in figure.
3. Switch on the motor.
4. Find the time required to complete ten revolutions by the block.
5. Repeat the same two to three times.
6. We observe that the wooden block moves in a circular path with a constant speed.
7. So, this motion of wooden block is called uniform circular motion.

Activity – 2

Question 2.
Define centripetal acceleration and derive an expression for centripetal acceleration.
Answer:
Centripetal acceleration :
The acceleration which can change only the direction of velocity of a body is called centripetal acceleration.

Derivation :

1. Let a body is in uniform circular motion.
2. Draw velocity vectors at successive time intervals as shown in the figure.
3. Transfer tails of each velocity vector to coincide at a single point without changing their direction as shown in the figure.
4. In the above figure, the directed line joining two vectors represents change in velocity (Av).
5. Let us consider the change in velocity during the course of a complete revolution of a body i.e., the sum of the magnitudes of the changes in velocity during a complete revolution will be equal to the sum of the sides of the depicted polygon.
6. The smaller the sides of our polygon, the closer they cling to the circle of radius v, consequently the magnitude of change in velocity of the body during the course of revolution, will be equal to the circumference ’2πv’ of the circle.

9) As the vertex angle of isosceles triangle decreases, the angle between the change in velocity approaches to 90°.

10) Therefore, the acceleration of a body in uniform circular motion is directed perpendicular to its velocity.

Activity – 3 Free fall

Question 3.
Accelerahon is independent of masses.
Place a small paper on a book. Release the book with the paper from certain height from the ground.
a) What is your observation?
Answer:
The book and paper will fall on the ground at same time, if the paper is kept in the book. If the paper is kept on the book and released, then the paper will be separated from book and falls on the ground little bit later than the book.

b) Drop the book and paper separately, what happens?
Answer:
Book reaches the ground first, then the paper reaches.

Activity – 4

Question 4.
What is the direction of ‘g’?
Throw a stone vertically up. Measure the time required for it to come back to earth’s surface with stop clock.

a) What happens to its speed when it moves up and down?
Answer:

• When the stone moves up, its velocity decreases gradually and finally it becomes zero, because it is moving against the direction of gravitation.
• When its velocity becomes zero, it starts to fall down due to gravitational force of earth, and its velocity increases.

b) What is the direction of acceleration?
Answer:

• While the stone is moving up, the direction of acceleration is in upward direction, which is against to the direction of gravitational force.
• While the stone is falling down, the direction of acceleration is in downward direction, which is in the direction of gravitational force.

Activity – 5

Question 5.
Describe the method of measuring the weight of a free fail body.
Answer:

• Take a spring balance and suspend it to the ceiling and put some weight to it.
• Note the reading of the spring balance.
• Now drop the spring balance with load from certain height to fall freely.
• Carefully observe the change in the position of indicator on the spring balance scale while it is in free-fall.
• We observe that the indicator of spring balance shows zero while it is in free-fall.
• This is due to the weightlessness of a free-fall body.

Activity – 6

Question 6.
How do you demonstrate the changes during the free-fall of a body?
Answer:

• Take a transparent tray and make holes on opposite sides.
• Take two or three rubber bands and tie them tightly, close to each other between the holes.
• Now place a stone on the bands as shown in the figure.
• We observe that the bands bend due to the weight of the stone.
• Now drop the tray with stone.
• We observe that the bands do not bend. They straight.
• When in equilibrium on a firm surface, weight is evidenced by a support force. Then weight equals to mg.
• When the body falls freely then it experiences weightlessness.
• Even in this weightless condition, there is still a gravitational force acting on the body causing downward acceleration.

Activity – 7

Question 7.
Give one activity that showing center of gravity and balancing.
(OR)
How do you balance spoon and fork?
Answer:

• As shown in the figure arrange a fork, spoon and wooden match stick together.
• The combination will balance nicely on the edge of the glass.
  The weights of the spoon and fork will pass through the centre of gravity and the base (glass).

Activity – 8

Question 8.
Can you get up without bending?
Sit in a chair comfortably as shown in figure. Try to get up from the chair without bending your body or legs.

a) Are we able to do so? If not why?
Answer:

1. We cannot get up from the chair without bending our body or legs.
2. When we sit in a chair, we are in weightless condition.
3. We need a support force to get up from the chair.
4. This support force can be obtained by bending our body or legs.

Activity – 9

Question 9.
How do you balance a ladder on your shoulder?
Answer:

• Take a ladder.
• Find the mid stick by counting the sticks of the ladder.
• Put that mid stick on the shoulder and balance the ladder.
• That is the center of gravity of a ladder.

Activity – 10

Question 10.
How can you locate the centre of gravity of a uniform object?
Answer:

1. Take a meter scale.
2. Suspend it from various points.
3. We observe that it bends to one side.
4. Suspend it from the mid point.
5. We observe that the scale will be in horizontal position without bending to any side.
6. At this point, the scale behaves as if its entire weight is concentrated at this point.
7. The support given at this single point gives support to the entire scale.
8. This point is its centre of gravity.

Activity – 11

Question 11.
Identifying the centre of gravity of a ring.
The center of gravity of any freely suspended object lies directly beneath the point of suspension.

If a vertical line is drawn through the point of suspension, the center of gravity lies somewhere along that line. To determine exactiy where it lies along the line, we have only to suspend the object from the some other point and draw a second vertical line through that point of suspension. The center of gravity lies where the two lines intersect.

a) Where does the center of gravity of a ring lie?
Answer:
The centre of gravity of a ring lies at its geometric centre.

b) Does the center of gravity of a body exist outside the body?
Answer:
For the bodies which are in right angled triangle shape, the centre of gravity falls out side the body. Hence we can say the CG of a body may be outside or inside the body.

c) Does center of gravity of an object exist at a point where there is no mass of the object?
Answer:
The centre of gravity exist at a point where there is no mass of the object, for the objects like annual rings.

Activity – 12

Question 12.
Shift of the centre of gravity and its effects.
Try to touch your toes as shown in figure (a). Try this again when standing against a wall as shown in figure (b).

a) Are you able to touch your toes in second case as shown in figure? If not why?
Answer:

• We cannot touch our toes in the second case as shown in figure.
• When we stand erect with the support of wall, the centre of gravity shifts its place from second sacral vertebra to the place near to abdomen.

b) What difference do you notice in the center of gravity of your body in above two positions ?
Answer:

• In the first position, the centre of gravity is at a place near to the centre of back-bone.
• In the second position, the centre of gravity shifts from the place near to the centre of backbone to the place near to abdomen.

AP State Syllabus AP Board 9th Class Social Studies Important Questions Chapter 9 Credit in the Financial System.

AP State Syllabus 9th Class Social Studies Important Questions 9th Lesson Credit in the Financial System

9th Class Social 9th Lesson Credit in the Financial System 1 Mark Important Questions and Answers

Question 1.
Expand NABARD. (SA-III : 2015-16)
(OR)
Explain the term NABARD. (SA-II : 2017-18)
Answer:
National Bank for Agricultural and Rural Development.

9th Class Social 9th Lesson Credit in the Financial System 2 Marks Important Questions and Answers

Question 1.
500 and 1000 rupees notes were demonetized recently. How far is this helpful for Indian economy in your opinion? (SA-III : 2016-17)
Answer:
The decision of the government to scrape 500 and 1000 currency notes is affecting different class of society in a different way.
Poor class :
This class is affected adversely immediately. Because they use debit or credit card is very less.

Temporarily they face problem but they become normal within month.

Middle class :
They too have to stand on a big queue for short time because they still need the 100 rupee note, for making petty payments.

Upper class :
They too may face trouble for few days but their life would become normal very soon.

Long term benefits :

1. Developmental activities would pick up significantly as the tax revenue increases.
2. Corruption would reduce.
3. Government can reduce rates of taxes.
4. Illegal activities would reduce.
5. Dowry and other social practices like extravagant marriages would reduce due to white economy.

Question 2.
What do the banks do with the deposits which they collect from the public? (SA-III : 2016-17)
Answer:

• Banks keep only a small proportion of their deposits as cash with themselves.
• Banks in India these days hold about 15% of their deposits as cash.
• This is kept as provision to pay the depositors who might come to withdraw money from the bank on any given day.
• Banks use the major portion of the deposits to extend loans.
• There is a huge demand for loans for various economic activities.

Question 3.
Financial literacy is the process of equipping oneself with knowledge and information on financial matters. Taking interest in financial literacy helps one to goals and protect oneself from frauds and debts traps. It aims inculate savings habits improve the understanding of financial products leading to effective use of financial services and thus helps better money management further financial literacy facilitates easy access to financial services.
“Financial literacy is an important for consumer protection and financial stability”? Comment on it. (SA-II : 2016-17)
Answer:
Importance of Consumer protection and Financial literacy :

1. Ensure that financial markets are deep and serve the broad population.
2. Provide access to financial services for low income households and
3. Ensure long-term stability in the financial system.
4. Financial markets help to build consumer trust in financial institutions and ensure that financial institutions reach out to serve the needs of the population, including low-income households that often lack access to basic financial services.

Question 4.
Appreciate the role of self-help groups to fulfill the financial needs of poor women. (SA-II : 2016-17)
(OR)
Self help groups are the building blocks of organisation of the rurql and urban poor. Not only do women become financially self reliant, it is a platform to discuss and act on a variety of social issues such as health, nutrition, domestic violence etc.”
Do you agree with the above statement? Explain your answer. (SA-II : 2018-19)
Answer:

• The Self Help Groups played a very significant role in empowering rural women in India.
• Self Gelp Group fulfill the commercial requirements of poor women members by doing the small amount of daily savings and making contributions for few months till the time there is sufficient funds in the group to start lending.
• To empower the women they provide buffaloes on loan, sewing machines, and provide loan for small general stores etc.
• Not only these the SHG group protect the women from domestic violence and from social abuse etc.
• SHG’s work for rural and urban poor women.

9th Class Social 9th Lesson Credit in the Financial System 4 Marks Important Questions and Answers

Question 1.
“There are some major differences between the way formal and informal credit providers operate in India. While the formal credit providers follow certain rules and regulations framed by government, informal credit providers do not follow such rules. When the borrower could not repay as per the agreed terms, formal credit providers cannot use any illegal ways to get back the credit, whereas informal credit providers use many coercive and illegal ways which at times lead to borrowers committing suicides. Compared to the formal lenders, most of the informal lenders charge a much higher interest on loans. Banks and cooperative societies need to lend more. This would lead to higher incomes because many people could then borrow cheaply for a variety of different needs. They could grow crops, do business, set up small-scale industries etc. They could set up new industries or engage in business activity. Cheap and affordable credit for all is crucial for the country’s development.”
Q. “The rich households are availing cheap credit from formal lenders whereas the poor households have to pay a heavy price for borrowing from informal sources” – Comment in your own words. (SA-III : 2016-17)
Answer:
The main reason behind poor house holds depends on informal lenders/sources because banks do not wish to give loans to the poor, who have no collateral. Bank loans require proper documents and collateral. Banks prefer not to lend money to the poor farmers and landless labourers, because more often than not they don’t have the required documents to take loan.

But rich people have more properties, they should submits proper documents to banks for loan.

According to this, rich people are benefited with low rate of interest but poor people are suffered with high rate of interest.
So formal sector loans need to expand in rural areas for the development of poor.

Question 2.
What are the various services provided by the bank to the customers? (SA-II : 2018-19)
Answer:
Financial institutions means banks may differ in the type and number of services they provide to customers.

The services most often provided include a variety of checking accounts, savings accounts; certificates of deposits, and loans, including car loans and home mortgages.

Additional services may include safe deposit boxes and investment related services. Education loans to students also.

9th Class Social 9th Lesson Credit in the Financial System Important Questions and Answers

Question 1.
What are the two important functions of Banks?
Answer:
All commercial banks perform the following two functions.

1. Banks accept deposits from the customers and pay an interest on the deposits.
2. Banks lend loans to the customers and charge interest on the loans.

Question 2.
What is the primary source of income for banks?
Answer:
The difference between what is charged from borrowers and what is paid to the depositors is the primary source of income for banks.

Question 3.
What is meant by the term ’credit1 (loan)?
Answer:

• Credit refers to an agreement in which the lender supplies the borrower with money, goods or services in turn for the promise of future payment.
• Credit helps us to meet our needs or expenses.

Question 4.
What is meant by the term collateral?
Answer:
Collateral is an asset that the borrower owns (such as land, building, vehicles, livestock, deposits with bank) and uses this as a guarantee to a lender until the loan is repaid.

Question 5.
What are formal and informal sources of credit in India?
Answer:

• The various types of loans can be conveniently grouped as formal sector loans and informal sector loans.
• Among them, formel are loans from banks and cooperatives.
• The informal lenders include moneylenders, traders, employers, relatives and friends, etc.

Question 6.
What is meant by the word ’financial literacy’?
Answer:

• Financial literacy is the process of equipping oneself with knowledge and understanding on financial matters and to take right financial decisions leading to financial confidence.
• Simply, taking efforts to equip oneself with knowledge on financial matter.

Question 7.
Where do we get information regarding financial literacy?
Answer:

• Financial literacy material is available on the website of Reserve Bank of India.
• In addition, for the benefit of word illiterate persons in rural and urban and remote areas, State Level Bankers Committee (SLBC), AP has prepared an audio CD on the benefits of saving with banks.

Question 8.
What are “the terms of credit”?
Answer:
Interest rate, collateral and documentation requirement and the mode of repayment together comprise what is called the terms of credit.

Question 9.
Why do you think bank deposits are called ‘demand deposits’?
Answer:

• Banks accept the deposits and also pay an amount as interest on the deposits.
• People have the right to withdraw the money as and when they require.
• Since the deposits in the bank accounts can be withdrawn on demand, these deposits are called ‘demand deposits’.

Question 1o.
Why do you think the people in rural areas demand for credit?
Answer:

• In the rural areas, the main demand for credit is for crop production.
• Crop production involves considerable costs on seeds, fertilizers, pesticides, water, electricity, repair of equipment, etc.
• Farmers usually take crop loans at the beginning of the season and repay the loan after harvest.
• There is usually 3 to 4 months gap between farmers buying inputs and selling the crop.
• Repayment crucially depends on income from farming.

Question 11.
Read the passage and answer the following questions.

The RBI has now initiated processes of improving the financial access to people in rural areas. All banks would be opening rural accounts using Business Facilitators and Business Correspondents. These correspondents would encourage people in rural areas to open bank accounts so that they can save their money and also use loan facilities of the bank. These facilitators would help them connect with the local branch. Electronic identification systems would be used to open these accounts. Recently, the government initiated providing Unique Identification Number to every citizen of India. All those who have enrolled themselves and given a card called Aadhaar. Those who have this number can open the bank account easily and also get the benefits and services provided by government. Earlier banks used to make it mandatory to put a minimum amount while opening an account. Nowadays, can open account and there is no compulsion to keep any minimum amount. This is called ‘Basic Savings Bank Deposit Account’ (BSBDA).

1) What has RBI initiated?
Answer:
The RBI has now initiated processes of improving the financial access to people in rural areas.

2) What would be the uses of RBI’s steps?
Answer:
They would encourage people in rural areas to open bank accounts, to save money ’ and also use loan facilities of the banks.

3) What initiations has the government taken recently?
Answer:
Recently, the government initiated providing unique identification number to every citizen of India.

4) What is the name of the card?
Answer:
Aadhaar card.

5) Is there any mandatory to put a minimum account?
Answer:
Now, there is no compulsion to keep a minimum amount. This is called ‘Basic Savings Bank Deposit Account’.

Question 12.
Understand the Pie diagram and fiSi the table.

Sources of credit for rural Households in India in 2003

Read the above table and Answer the following questions.
1) Note the change in the loans issued by all formal organizations for the last three decades.
Answer:
The loans issued by formal organizations has increased from 15.8% in 1961 to 52% in 2003. There is an increase of 36.2%.

2) What was the difference in the loans issued by all informal organizations for the last three decades?
Answer:
The loans issued by informal organizations have been reduced from 84.0 to 48%. There is a decrease of 36%

Question 13.
What are the reasons for farmers distress in Andhra Pradesh?
Answer:

• Most of the farmers take loans to meet the expenses of cultivation.
• When crops fail, they cannot repay the loans.
• Again they take a fresh loan from informal lenders.
• Finally fallen in debt-trap and this leads to distress among them.

Question 14.
What are the reasons for the poor notable to get bank loans, nowadays?
Answer:

• Bank loans require proper documents and collateral.
• Absence of collateral is one of the major reasons which prevent the poor from getting bank loans.
• They have a few assets to keep as collateral.
• They are going to easily accessible informal loans.

Question 15.
How is cheap and affordable credit for all, crucial for the country’s development nowadays?
Answer:

• Borrowing at higher rates of interest makes borrowers to have left with less income for themselves.
• In somecases it may be more than his income and leading to debt trap.
• For this reasons, banks and cooperatives need to lend more.*
• As these offer loans at lower rate of interest, borrowers use them for a variety of needs.
• Thus the availability of cheap and affordable credit for all is crucial for the country’s development nowadays.

Question 16.
Study the following pie-chart.

1) What does the above chart describe?
Answer:
It describes the distribution of credit among different households.

2) Describe the pie-chart.
Answer:

• Out of total credit, poor households take 40% of the credit.
• Out of total credit, rich households take 21% of the credit.
• Well-off households take 32% of credit and stood 2nd place in availing credit.
• Households with few assets take least percentage of loans, i.e. only 7%.

Question 17.
What is the measure taken by government and Non-governmental Organizations to organize rural poor?
Answer:

• In recent years government and NGOs have found new way for providing loans to the poor.
• The idea is to organize rural poor, particularly women into small Self Help Groups (SHGs) and pool their savings.
• SHGs with 15-20 members save Rs. 25 to Rs. 100, at least for 2 years.
• They can take small loans from group itself to meet their needs.
• Group charges small interest on borrowing members.
• After a year or two, they can get loan from bank without collateral.

Question 18.
What are the measures taken by RBI to help rural agriculture?
Answer:
1) The Reserve Bank of India sees that banks give loans not just to profit making business and traders but also to small cultivators, small scale industries, to small borrowers, etc.

2) In recent times, besides RBI, NABARD (National Bank for Agricultural and Rural Development) facilitates formal credit organisations in Rural India.

AP State Syllabus AP Board 9th Class Social Studies Important Questions Chapter 1 Our Earth.

AP State Syllabus 9th Class Social Studies Important Questions 1st Lesson Our Earth

9th Class Social 1st Lesson Our Earth 1 Mark Important Questions and Answers

Question 1.
Which continent is extended in four hemispheres In the given map. (SA-III : 2015 – 16)
Answer:

Africa continent.

Question 2.
What do you mean by anti meridian? (SA-III : 2016 – 17)
Answer:
The anti meridian is the meridian of longitude opposite the Prime-Meridian.

9th Class Social 1st Lesson Our Earth 2 Marks Important Questions and Answers

Question 1.
Draw the picture of the Globe and point out all the latitudes that are given special names on it. (SA-III : 2016 – 17)
Answer:

Question 2.
Why is it important to know the latitude and longitude of a place on map? How can it be useful? (SA-II : 2018 – 19)
Answer:
It is very important to know about latitudes and longitudes of a place by the following reasons.

• The particular location of a place on the earth can only be traced precisely with the help of latitude and longitude of that place.
• Latitude also help us in understanding the pattern of wind circulation on the global surface.
• Longitudes are useful to us to define the east-west position of a location on the planet.
• Longitudes are useful to us to know the time of the place.

Question 3.
Wegener hypothesised that the super continents of pangea broke up into two blocks –
1) Laurensia
2) Gondwana. It took millions of years for the continents to reach the present shapes and positions on the globe. (SA-I : 2018 – 19)
1) Laurensia : North America, Greenland, and all of the Eurasia north of Indian sub continent.
2) Gondwana : South America, Africa, Madagascar, India, Arabia, Malaysia, East Indies, Australia and Antartica.
Based on the above information given – answer the following questions.
a) Write any two land masses of present Asian continent which were formed from Gondwana?
b) From which block was the present Europe continent formed?
Answer:
a) India, Arabia, Malaysia, East Indies.
b) The present Europe continent was formed from Laurensia block.

Question 4.
If every state in India follows its local time then what problems will arise? (SA-I : 2019 – 20)
Answer:
If every state follows its local time, the following problems will arise :

• People travelling to different states would have to change their clocks too often.
• There would be confusion and chaos in the timings of railways, airlines, buses etc.
• The schedules of television shows, live shows and games, news etc. would be disrupted.

9th Class Social 1st Lesson Our Earth 4 Marks Important Questions and Answers

Question 1.
What is the difference between local time and standard time ? If every state follows its local time then what problems will rise in India? (SA-III : 2015 – 16)
Answer:
Difference between Local and Standard time:

Local Time	Standard Time
1) The time of a place when the mid day sun is over head is called local time.	1) The local time of the standard meridian of a country is called a standard time.
2) It changes from place to place.	2) It remains same for that particular country.
3) The place on the same longitude has the same local time.	3) The place on the same longitude has the different standard time.

Example:
If the IST is 12.00 noon, the local of Mumbai is 39 minutes – IST = 11.21 minutes a.m. Since Mumbai is on 72°82′ east longitudes, it is 9°45′ behind the 82°30′. Thus the local time of Mumbai is 9.45 x 4 = 38 minutes.

If every state follows its local time, a lot of serious problems would rise. Some of them are being discussed hereunder.

• At the time of national calamities and disasters, it is very difficult for the national government to make necessary emergency announcement.
• At the time of wars and national emergency it is very difficult for the national government to alert all the defensive forces stationed in all the state capitals and the naval forces of all the coastal states.
• It is very difficult for Televisions and Radios to follow a single schedule to broadcast their programmes.
• Railways faces a difficult problem in preparing a timetable for its trains that travel through many states.

Question 2.
Describe the internal structure of the earth. (SA-III : 2016 – 17) (SA-I : 2018 – 19)
Answer:
The earth is made up of three main layers.
A) Crust:

1. The outer part of the earth on which we live is called the crust.
2. While the earth was boiling in a molten form the lighter particles cooled at the top and formed the layer of crust.
3. The curst mostly consists of various kinds of rocks.
4. This layer goes up to a depth of 30 to 100 kms.

B) Mantle:

1. While the earth was boiling in a molten form the less heavier particles settled in the middle and formed the mantle.
2. The upper part of the mantle is a pliable layer over which the crust floats.
3. This layer consists mainly of chemicals called silicates.
4. It exists at the depths from 100 kms to 2900 kms.

C) Core:

1. While the earth was boiling in a molten form the heaviest substances formed core.
2. It is composed of dense and heavy substances like Iron and Nickel.
3. It exists at the depths from 2,900 kms to 6,376 kms.
4. It can be divided into two sub-layers.

a) Outer core :
This layer is composed of liquid metallic material like nickel and iron. It is 2,900 – 5,100 kms in thickness.

b) Inner core :
The solid inner core is made up of iron compounds and heavy substances like gold. It is 5,100 – 6,376 kms in thickness.

9th Class Social 1st Lesson Our Earth Important Questions and Answers

Question 1.
How can you say the man himself is responsible for environmental crises?
Answer:

• More than any other animal human beings have been trying to make the earth a better place to live in.
• Trying to change ourselves and our surroundings we have entered into conflict with other inhabitants of the earth.
• For long we’ve been exploiting the earth for its resources.
• The reckless exploitation of the earth resulted in environmental crises such as global warming and poisoning of our soils, water and air.
• Thus we can say man himself is responsible for environmental crises.

Question 2.
What were the initial ideas of people about the earth, the sun the moon and other astronomical bodies?
Answer:

• For thousands of years humans have been looking into the sky trying to understand objects that shine there.
• Initially, people thought that earth was firm and stationary and all others went round it.
• They also thought that the earth, the stars and the sun have been like this forever and will be like this forever without any change.

Question 3.
Write about the phases of evolution of facts, about the astronomical bodies their birth and growth.
Answer:

• Initially, people were of the view that the earth was firm and stationary and all the other bodies went round it.
• About five hundred years ago scientists concluded that the earth is not in the middle of everything.
• The earth actually moves round the sun and that the sun itself is also moving.
• The countless stars in the sky are actually so many suns.
• During the last hundred years or so people learnt the stars are born, they grow old and even die.
• Scientists even came to know that the stars are actually part of larger groups called galaxies.
• There are millions of galaxies in the universe.
• Now scientists are of the view that the universe itself started some 13.7 billion years ago with a Big Bang and it may end several billion years later.

Question 4.
How dkl the universe come into existence?
Answer:

1. The universe itself started some 13.7 billion years ago with a Big Bang.
2. From this Big Bang, several galaxies were formed.
3. Within these galaxies, stars were formed.
4. Planets were formed around stars and went around them.

However these astronomical changes take place over thousands and even millions of years.

Question 5.
Describe the process of evolution of the Earth.
(OR)
How did the earth come into existence and get its present form?
Answer:

• The earth began to form around four and a half billion years ago.
• It began as a ball of swirling dust and clouds and passed through a molten age.
• Gradually it grew in size.
• It was very hot and was in molten stage.
• The lighter particles cooled at the top and formed a layer of crust.
• Heavier particles formed the part of the molten core.
• As the earth’s interior cooled and contracted, the outer crust wrinkled, forming ridges and basins.
• The rain filled the basins and thus oceans formed.
• Slowly atmosphere developed and slowly life appeared on the earth.

Question 6.
How and when did the life appear on earth?
Answer:

• Different kinds of gases including water vapour formed the atmosphere on earth.
• Most of these gases were such that life as we know it today could not survive on it.
• Because it did not have oxygen necessary for life to survive.
• It took a long time for the air to develop.
• Then life appeared on oceans first.

It slowly evolved into diverse forms – plants, animals and human beings.

Question 7.
Are the shapes and positions of the continents fixed and permanent as they appear on the globe?
Answer:
The shapes and positions of the continents may seem fixed at the time scale of human experience. But on old earth continents have moved, collided, merged and then been torn apart again.

Mountains have risen and been razed to the ground, oceans have formed and dried up. Valleys have been carved and so during the course of earth’s eventful history. Alfred Wegener’s theory of Continental drift proves the same idea.

Thus the shapes and positions of the continents are not fixed and permanent.

Question 8.
Describe the theory of continental drift.
Answer:

• In 1912 Alfred Wegener propounded the theory of continental drift to describe the present arrangement of continents and ocean basins.
• He postulated a massive super continent Pangaea that existed 220 million years ago.
• Pangaea, the hypothetical continent, from which present continents originated by the drift from Mesozoic era to the present.
• Wegener hypothesized that the super continent of Pangaea broke up to from :
  a) Laurensia – consisting of present North America, Greenland and all of Eurasia north of Indian subcontinent and
  b) Gondwana land – consisting of present South America, Africa, Madagascar, Arabia, India, Malaysia, East Indies, Australia and Antarctica.
• These two blocks were separated by a long shallow inland sea called Tethys sea.
• It took millions of years for the continents to reach the present shapes and positions on the globe.
• Even today many of the continents are moving very slowly pushing each other.

Question 9.
What do you know about latitudes?
Answer:

• Latitudes are imaginary lines drawn around the earth.
• The word ‘latitude’ comes to us from the Latin word ‘iatitudo’ meaning width.
• Latitudes are also called parallels because they are parallel to each other.
• Latitudes are circles.
• Latitudes are expressed in degrees (°), minutes (‘) and seconds (“).
• Latitude values range from 0° t* 90° North (the North Pole) and 90° South (the South Pole).
• Thus there are 180° main latitudes (not counting the equator)
• Equator, the 0° latitude is the largest among all the latitudes.
• Latitudes are used together with the longitudes to locate a place on the earth.
• Latitudes are used to locate the climatic zones on the earth.

Question 10.
What do you know about longitudes?
Answer:

• Longitudes are imaginary lines connecting North and South’Poles.
• Longitudes are semi-circles.
• Longitudes are also called meridians because when the sun is overhead on a longitude at the time on that longitude it is noon (meridianus).
• There are 360 longitudes in total.
• The longitudes from 0° to 180° to the east are called eastern longitudes.
• The longitudes from 0° to 180° to the west are called western longitudes.
• 0° meridian is called the Prime meridian or Greenwich meridian.
• Longitudes are also expressed in degrees (°), minutes (‘) and seconds (“).

Question 11.
How are the time zones formed and why are they formed?
Answer:

• It takes 4 minutes for the sun’s position to move 1° of longitude.
• This means that the time is different for each degree of longitude.
• This can cause a lot of confusion.
• Therefore to end up this confusion the world is divided into 24 time zones.
• The width of each time zone is 15° of longitude.
• This means the difference between one time zone and the next is 1 hour.
• As you go from Greenwich meridian, you add time; as you go west of the Greenwich meridian you subtract time.

Question 12.
Why does every country have its own standard time?
Answer:

• The world is divided into 24 time zones.
• The width of each time zone is 15° of longitude.
• This means that the difference between one time zone and the next is one hour.
• Some countries would have more than one time zone with less than one hour division.
• This is considered too complicated to be useful.
• That is why some countries choose the time along one of the meridians that pass throught their territory and follow the time of that meridian for the whole country.
• This time is called standard time.

Question 13.
What is a Grid?
Answer:
A grid is a square or a rectangle that is formed between when two latitudes and longitudes out across each other. In other words, the network of latitudes and longitudes drawn on the globe is called a ‘grid’.

Question 14.
When it is 12 noon in Greenwich (0°), what is the local time at Mumbai (73° E)?
Answer:
Mumbai (73° E) : Local time at Mumbai is : 73 x 4 = 292 minutes, i.e. 4 hours 52 minutes. That means the local time at Mumbai is 4 hours 52 minutes after 12 noon i.e., 12.00 + 4.52 = 4.52 p.m.

Question 15.
When it is 12 noon in Greenwich (0°), what is the local time at Chicago (87°30′ W) ? Chicago (87°30‘ W) : Local time at Chicago is : 87°30‘ x 4 = 350 minutes, i.e. 6 hours 50 minutes. That means the local time at Chicago is 6 hours 50 minutes less than 12.00 noon at Greenwich.
i.e. 12.00-6.50 = 5.10 a.m.

Question 16.
When it is 12 noon in Greenwich (0°), what is the local time at Sydney (151° E)?
Answer:
Sydney (151° E): Local time at Sydney is 151° x4 = 604 minutes, i.e. 10 hours 4 minutes before Greenwich time.
That means the local time at Sydney is 12.00 + 10.04 = 10.04 p.m

Question 17.
a) What are called ‘parallels’?
b) What are called ‘meridians’?
Answer:
а) Latitudes are called ‘parallels’,
b) Longitudes are called ‘meridians’.

Question 18.
What is the standard meridian of India?
Answer:
82°30′ Eastern longitude is the standard meridian of India.

Question 19.
If you were to travel from India to Japan. How would be the change in time?
Answer:

1. Japan is located in East to India.
2. If we travel to East, then we gain time as per East Gain Add (EGA).
3. India is in 5Vi hours time zone and Japan in 9 hours time zone.
4. Both are in eastern hemisphere. Thus we gain nearly 3% hours time.

Question 20.
How do you think human greed led to exploitation of the earth?
Answer:

• Human life on earth dates back to one lakh years, whereas formation of the earth was four and a half billion years ago.
• Man has constantly trying to change our surrounding to make it a better place to live in.
• He looked on earth as a storehouse of resources and making use of it, at will.
• Thus his greed led to exploitation of the earth.

Question 21.
Why do you think, it took so long time to understand the interior of the earth?
Answer:

• It is difficult for man to know directly about the Earth’s interior.
• So far man could dig a 3 km interior of the earth.
• He could send pipes upto a depth of 6K km.
• But, the radius of the earth is 6,440 km.
• Apart from this, if we go deep the earth-temperature raises at a rate of 1°C for every 32 meters.
• An estimated temperature at the centre of the interior of the earth is 6000°C.
• Thus man was unable to get direct information.
• So he need to rely on indirect sources like seismic waves etc.
• Thus it took so long time to understand the interior of the earth.

Question 22.
Describe the earth’s interior.
Answer:

1. The earth has a radius of 6440 km.
2. The temperature increases at a rate of 1°C for every 32 mts. of depth.
3. The temperature at the centre of the earth would be 6000° C.
4. As such the rocks will be in molten stage.
5. Pressure also increases when one goes deeper into the earth.
6. The earth is made up of three layers. They are : 1) Crust, 2) Mantle, 3) Core.
7. These layers differ from one another in thickness and also in their physical and chemical compositions.

Question 23.
What is “continental drift theory”? Explain.
(OR)
What is the “theory of continental drift”?
Answer:

• Alfred Wagener postulated the theory of continental drift.
• It explains the present arrangement of continents and ocean basins.
• He postulated a massive super continent called “Pangaea” which existed 220 million years ago.
• Present continents originated, by the drift from this “Pangaea”.
• Wagener hypothesised that the supercontinent of Pangaea broke up into two blocks
  1) Laurensia,
  2) Gondwana land.
• The two blocks were separated by a long shallow inland ocean called “Tethys”.
• It took millions of years for the continents to reach the present shape and position.

Question 24.
Differenciate between latitudes and longitudes.
Answer:

Latitudes	Longitudes
1. Latitude comes from a Latin word “Latitudo”, meaning width.	1. Longitude is derived from a Latin word “Longitudo”, meaning height.
2. The circles drawn parallel to the equator at 1° interval are known as latitudes.	2. The semicircles drawn connecting pole to pole are known as longitudes.
3. There are 180 latitudes excluding the equator.	3. There are 360 longitudes.
4. Every latitude must be designated with either “N” or “S” direction.	4. Every longitude must be designated with either “E” or “W” direction.
5. They are also known as “Parallels”.	5. They are also known as “Meridians”.
6. The climate of a place can be identified with the help of latitudes.	6. The differences in time can be calculated with the help of longitudes.

Question 25.
How many blocks did the Pangaea brake up into? What are they?
Answer:
The super continent of Pangaea was broke up into two blocks.
1) Laurensia:
Present N.America, Greenland and all of Eurasia, north of Indian subcontinent formed from it.

2) Gondwana land :
Present S.America, Africa, Madagascar, India, Arabia, Malaysia, East Indies, Australia and Antarctica formed from it.

Question 26.
How do you find a place in an atlas?
Answer:

1. We can find the information about a place in an atlas with the help of latitudes and longitudes.
2. Places are listed alphabetically at the back of the atlas.
   Ex : To locate “Visakhapatnam”.

Question 27.
What are longitudes? How many are there? Name some important longitudes.
Answer:

1. The semicircles connecting pole to pole are called longitudes.
2. They are 360 in number.
3. Some important longitudes are :
   a) Prime Meridian – 0° longitude
   b) International Date Line – 180° longitude

Question 28.
“For long we have looked at the Earth as a store house of resources, which we can exploit and use at will. Gradually we are realizing the fallacy of this view point” – Interpret the above statement.
Answer:
For long we have looked at the earth as a store house of resources. With this view we recklessly exploited the earth and are responsible to the destruction of forests, rivers, hills, fellow animals and even fellow humans. This resulted in the environmental crises such as global warming and poisoning of our soils, water and air.

But gradually we understand that the earthly resources are not infinite but finite and the environmental system is a closed one. So we should not use the natural resources indiscriminately.

If a man has to survive, he must derive something from the nature. The exploitation of minimum resources from the natural environment to fulfil the basic needs of human society would cause disequilibrium of some sort in the ecological balance resulting into environmental degradation and pollution. We should always use the natural resources in such a way that they are always at available in a desired quantity and quality.

Question 29.
“Today more than any other time we need to build a new understanding of the Earth, how it works and what we do on it and what we do with each other” – Interpret the above statement.
Answer:
In the decades of 1970s there emerged a concern about the fear of depletion of natural resources because of irrational and rapacious utilization of natural resources. This serious concern arises from the fact-rapid rate of rapacious exploitation of natural resources and modern production processes and advanced technologies. Thus the exploitation of natural resources has threatened the stability and survival of natural ecosystems and existence of several plant and animal species.

Hence today more than any other time we need to build a new understanding of the earth, how it works and what we do on it and what we do with each other.

Question 30.
Read the following para and answer the questions.
Scientists have figured out that the stars are actually part of larger groups called galaxies and that there are millions of such galaxies in the universe. Now, they are of the view that the universe itself started some 13.7 billion years ago with a ‘Big Bang’ and that it may end several billion years later.
1) What is a galaxy?
Answer:
A larger group of stars is called a galaxy.

2) When was the ‘Big Bang’ happened?
Answer:
‘Big bang’ was happened some IB.7 billion years ago.

3) How many galaxies are contemplated by scientists?
Answer:
Scientists contemplated that there are millions of galaxies in the universe.

4) When would be the end of the universe?
Answer:
The end of the universe would be after several billions of years.

Question 31.
What factors determine the number of standard times of countries?
Answer:
Countries which have much east-west extension will have a number of standard times.
Ex: Russia.

Question 32.
Identify other names of “Earth”.
Answer:
Bhoomi, Prudhvi, Dharithri, Dharani, Pudami, etc.

Question 33.

Layer of Earth	Depth	Composition
1. Crust	30 – 100 km	Various kinds of rocks
2. Mantle	100 – 2900 kms	Chemicals & Silicates
3. Outer core	2900-5100 kms	Nickel & Iron
4. Inner core	5100 – 6376 kms	Iron compounds & Gold

Observe the table and answer the following questions.
1) Which is uppermost layer of the interior of the earth?
Answer:
Crust is the uppermost layer of the interior of the earth.

2) What is the thickness of the core?
Answer:
The thickness of the core is 3476 kms.

3) Which layer is supposed to have more gold?
Answer:
The inner core is supposed to have more gold.

4) What is the radius of the earth?
Answer:
The radius of the earth is 6376 km.

Question 34.
Observe the following table and answer the questions given below.

What is the latitudinal value of “Equator”?
Answer:
The latitudinal value of Equator is “0°”.

2) What is the name given to 90° N and 90° S latitudes?
Answer:
90° N is called North pole and 90° S is called South pole.

3) What are the values of Arctic and Antarctic circles ?
Answer:
The value of Arctic circle is 6634° N.
The value of Antarctic circle is 6634° S.

4) In which hemisphere is the Arctic circle situated ?
Answer:
Arctic circle is in Northern hemisphere.

5) Which latitude does not have any direction?
Answer:
The Equator does not possess any direction.

Question 35.
One among our ‘environment crises’ is the poisoning of air. in light of this, how would you assess the Government of Delhi, deciding to allow vehicles with odd and even number plates on alternate days?
Answer:

• Air pollution is one among the environmental crises we face.
• Government of Delhi decided to allow the odd number plate vehicles to ply on the Delhi roads the other day.
• This alternate day journey provision definitely reduces the traffic congestion.
• It also promises in reduction of pollution.
• Already petrol vehicles ply on Delhi roads was banned.
• Compressed Natural Gas is the need of the hour.
• However, care must be taken to disallow everyone to have a vehicle with odd number and another with even.

Question 36.
Observe the following pictures.

a) What do the above pictures represent?
Answer:
The above pictures represent the stages of continental drift.

b) Look at the above picture “2” and identify the following.
1) India,
2) Africa,
3) Tethys sea

c) Identify.
i) South America in picture “3”.
ii) Antarctica in picture “4”.
Answer:

Question 37.
How can you say the Earth’s orbit is nearly circular but not exactly circular or an elongated oval path?
Answer:

• The orbit is the path of the Earth around the sun.
• The difference between earth’s farthest point (about 152 million km from the sun and the closest point 147 million km) is very small.
• Thus we can say the earth’s orbit is nearly circular but not exactly circular or an elongated oval path.

Question 38.
Prepare a palmphet on environmental crises.
Environment Crises
Answer:
For longtime man looked on earth as a store house of resources and tried to exploit at will. His reckless exploitation of earth has meant distruction of forests, rivers, hills, fellow animals and even fellow human beings.

Global warming, which is caused by the increased presence of green house gases like carbon dioxide, methane etc. It is resulting in melting of ice and submerging of low lands and coasts.

Soil pollution is caused by excessive use of chemicals, fertilizers and pesticides in agriculture and industrial waste deposition. Soil erosion is caused by excessive falling of trees and lack of pastures.

Water pollution is caused by routing of industrial wastes into water, usage of chemicals and pesticides etc. Air pollution is caused by the emissions from vehicles, air conditions etc.

Question 39.
Create visual representation to understand the time as described in the earth’s origin to your birth.
Answer:

AP State Syllabus AP Board 9th Class Social Studies Important Questions Chapter 8 Service Activities in India.

AP State Syllabus 9th Class Social Studies Important Questions 8th Lesson Service Activities in India

9th Class Social 8th Lesson Service Activities in India 4 Marks Important Questions and Answers

Question 1.
‘Service sector is beyond the other two sectors in providing employment’.
“Ramesh is a self employee who established an internet centre after completion of B.Tech. He also provided employment for two more persons”.
‘Service sector plays key role in providing employment’ comment on it. (SA-III : 2015-16)
Answer:
Yes. Services sector plays key role in providing employment by the following ways.

1. There has been tremendous change in the communication technology which has opened a wide range of jobs for educated people.
2. Business Process Outsourcing (BPO) has brought in new kinds of employment opportunities.
3. They provide services to people located across the globe using telecommunication links.
4. The entertainment industry creates jobs to work in various print media firms, cable television channels.
5. We see number of internet cafes and telephone booths in most of the cities and towns.
6. The advertising industry has also brought new job opportunities.
7. Many new jobs are available in Banking and insurance sectors.

Hence service sector can reduce educated unemployment in our country.

Question 2.
The table below shows the number of workers (in lakhs) employed in different service activities in large government enterprises in 1991 and 2010. Study the table and answer the question given below. (SA-II : 2018-19)

Service sector activities	Government jobs
	1991	2010
Wholesale and retail trade	1.5	1.7
Transport, storage and Communications	30.3	25.3
Finance, insurance, real estate etc.	11.9	14.1
Community, social and personal services	92.3	90.5

a) Which service activity provided least employment?
b) Write any two jobs related to community, social and personal services.
c) What kind of service activity jobs have shown maximum decrease in 2010?
d) What kind of service activity jobs has government-generated most in 2010?
Answer:
a) Wholesale and retail trade

b)

1. Washing and drycleaning work
2. Beauty treatment
3. Tailoring work
4. Barbour work (Hair cutting)
5. Who runs the photo studio.

c) Transport, storage and communications.

d) Finance, insurance, real estate etc.

9th Class Social 8th Lesson Service Activities in India Important Questions and Answers

Question 1.
How is service sector different from other sectors?
Answer:

• Other sectors, agriculture and industry produce goods that are tangible.
• But service activities do not produce any tangible good.
• But service activities fulfill the needs cater the requirements of people or organisations.
• They are also essential for agriculture and industrial activities.
• Non-production of commodity or good is the essential nature of service sector.

Question 2.
Is service sector, the heaven of dream jobs?
Answer:

• No, I don’t think so.
• Dream jobs in service sector are at a rate of one in tens of thousands of jobs.
• Remaining, especially uneducated and less educated do jobs with meagre wages.
• Those who have dreams are also under constant pressure and job stress.

Question 3.
Read the following case history and answer the following questions.

My lifestyle has improved due to IT. In college, I had just two trousers and two shirts. Now, I have many shirts. I buy good quality clothes and I don’t have to think about how much I spend. So definitely, working in the software industry has added comfort to my life. Earlier, there were a lot of financial problems in the family – my brothers and sisters were not able to study properly due to this, and I am very happy that I have been able to solve this problem. But it is a stressful and mechanical life; there is no social life. In my hometown, people were always there around me – neighbours and relatives. There was always someone to go and talk to but here, it’s difficult to make friends.

1) What was the position of the family before getting a job?
Answer:
Earlier there were a lot of financial problems in the family – his brothers and sisters were not able to study properly due to this.

2) What is his family’s financial position now?
Answer:
Working in software has added comfort to his life, and his brothers and sisters are able to study properly now.

3) Is the individual happy with his lifestyle?
Answer:

• He is earning good salary and that added comfort to his life.
• But at the same time the job is very stressful and his life is mechanical.
• He is missing his village, neighbours and relatives.

Question 4.
What is the work going on here in the given picture? Describe it in five sentences.
Answer:

1. It is a call centre job.
2. A call centre is an office where people work answering or making telephone calls for a particular company or customer regarding certain information.
3. The information may be regarding customer’s bank deposits or about their hospital records.
4. There will be three shifts and employees may have to work during nights too.
5. Salaries are high and at the same time lots and lots of stress in the job can be experienced.

Question 5.
What services, in your opinion, are desired today?
Answer:

• India faces an acute shortage of skilled human resources in the health sector. So health services are desired today.
• More infrastructure service is the need of the hour. So roads, hospitals and educational institutions are to be set up.
• We need good storage facilities as well as credit facilities.
• New economic policies in India shall emphasize the expansion of service activities.

Question 6.
Why do you think more people are engaged in low income service activities today?
Answer:

• With lack of job opportunities many people today are employed in low income services.
• Closure of factories forced workers to work as small vendors, rickshaw pullers and other low income service professions.
• People from rural areas are not getting opportunities in urban areas.
• They shift to many unskilled low earning employment opportunities in services.

Question 7.
Many unskilled have low earning employment opportunities in service sector. State your opinion.
Answer:

• People from rural areas come to work in the city but there are not enough employment opportunities in urban areas.
• Hence most of the unskilled are earning their livelihood as small vendors, rickshaw pullers, etc.
• They are unable to make both ends meet.

Question 8.
New job opportunities are depressing the employees. Comment on it (especially in IT).
Answer:

• New jobs are providing good salaries but the employees are also expected to work very long hours.
• The life is very stressful and mechanical.
• There is no social life.
• These jobs definitely depress the employees.

Question 9.
What measures are taken by companies to reduce cost and avoid paying benefits to workers?
Answer:

• In order to reduce cost and avoid paying health, pension and provident fund benefits to workers, industries ‘outsource’ security services to security agencies.
• Many companies outsource their work for research and development, accounting, legal services, customer service, public relations etc.

Question 10.
Many people work in service jobs. Few people do voluntary service. What measures would you take to distinct them?
Answer:

• Voluntary service means that is done free of cost or out of love and devotion.
• It doesn’t contribute to their livelihood.
• They have other occupation but do this as charity.
• On the otherhand, the people who work in service sector earn livelihood through it.
• They do specialised services required for people or organisations.

AP State Syllabus AP Board 9th Class Social Studies Important Questions Chapter 7 Industries in India.

AP State Syllabus 9th Class Social Studies Important Questions 7th Lesson Industries in India

9th Class Social 7th Lesson Industries in India 1 Mark Important Questions and Answers

Question 1.
Study the map given below and answer the following question. (SA-II : 2018-19)

Q : Where in Karnataka are the steel plants located?
Answer:
Vijayanagar and Bhadravathi are the two places has steel plants in Karnataka.

9th Class Social 7th Lesson Industries in India 2 Marks Important Questions and Answers

Question 1.
Draw a bargraph based on the given information. (SA-III : 2015-16)

Year	Production of cement (In million tonnes)
1970 – 71	25
1980 – 81	50
1990 – 91	100
2000 – 01	150
2010-11	210

Answer:

Question 2.
The pie charts below show the percentage of people employed in Agriculture. Industry and service sectors. Read the pie charts carefully to answer the question.

How did the pattern of employment change between 1972-73 and 2009-2010? (SA-II : 2018-19)
Answer:

1. The employment generation in agricultural sector has been decreased from 74% in 1972-73 to 53% in 2009-10.
2. The employment generation in industrial sector has been increased from 11% in 1972-73 to 22% in 2009-10.
3. The employment generation in service sector has shown an increase of 10%.

9th Class Social 7th Lesson Industries in India 4 Marks Important Questions and Answers

Question 1.
Observe the ‘Pie Chart’ and answer the following questions. (SA-III : 2015-16)

Answer the following Questions.
1. What does the above given graph denotes?
2. What is the percentage of change in employment by industry when compare between 1972-73 and 2009-10?
3. Which sector generated highest employment in 2009-10?
4. Write any two occupations regarding service sector?
Answer:

1. The above graph explains % of employment in different sectors.
2. From 1972-73 to 20019-10 the change in employment in Industrial sector is from 11% to 22%.
3. Agricultural sector.
4. Doctor, lawyer, teacher, banking, commerce, communications etc. are the occupations in the sector.

Question 2.
“Industries are necessary for the development of a nation. It is also fact that industrial activities are increasing environmental problems” – Write your opinions on this matter in detail. (SA-III : 2016-17)
Answer:
Industries are necesary for the development of a nation by the following ways.

1. When goods made in factories and exported to other countries, we get revenue.
2. A few decades before, three-fourths of income from goods exported from manufacturing industries alone.
3. Even today, nearly two-third of goods exports is contributed by industries and particularly small industries.
4. Factory goods exported range from gems, jewellery, chemicals, cars, machinery, cashewnuts, etc.
5. The money or foreign exchange earned in this process enable us to import from other countries a large number of goods that we want from other countries.

At the same time industrial activities are increasing environmental pollution by the following ways.

1. The production process in industries involves the use of electricity and application of different chemicals.
2. In the course of production, these industries release a lot of other materials. They are causing pollution in the industrial locations.
3. The industrialization led to the indiscriminate exploitation of minerals, forests, soils, air, etc.
4. It leads to deforestation and damages the natural habitat of animals.
5. Underground water is being contaminated due to the release of wastes by the industries.
6. Some animals are endangered and some creatures have become extinct.
7. The depletion of ozone layer, pollution of water, air, soil has increased ecological problems.

Question 3.
Mixing of some poisonous substances in air, water and soil causes to ‘ecological crisis’ – give your suggestions to prevent this problems as a student. (SA-II : 2017-18)
Answer:
Pollution prevention is a major global concern because of the harmful effects of pollution on a person’s health and on the environment.
Suggestions:

1. Stop smoking or at least follow the “No smoking” sign.
2. Never use open fires to dispose of wastes.
3. Instead of using your cars, choose to walk or ride a bicycle whenever possible.
4. Adopt the BRs. of solid waste management, reduce, reuse and recycle.
5. Use eco-friendly or biodegradable materials instead of plastic.
6. Do not cause loud noises and unwanted sounds to avoid noise pollution.
7. Industries should use fuel with lower sulphur content.
8. Industries should strictly follow applicable government regulations on pollution control.

Conclusion :
Breathing is life. We know that we will survive without food for several weeks and without water for few days, but without oxygen, we will die in a matter of minutes.

The oxygen, the air we breathe sustains us. So, let us make today and every day a good day for everyone.

Question 4.

Read the above pie chart and answer the following questions. (SA-II : 2017-18)
1. What does the pie chart tell us?
2. Which sector provide the highest percentage of employment?
3. In which sector employment increased twice?
4. By 2009-10 which sector was the second piace in empioyment?
Answer:

1. Pie chart tells us the percentage of employment in different sectors from 1972-73 to 2009-10 years.
2. Agriculture sector provide highest percentage of employment.
3. In Industrial sector employment increased twice.
4. By 2009-10, the services sector is in second place in employment.

Question 5.
When people buy groceries, they may have their groceries packed in plastic bags, paper bags, or cloth bags they bring with them.
Which type of grocery bag is the best to help protect the environment?
a) Plastic
b) Paper
c) Cloth
Explain in what way your choice of bag can help protect the environment.
Answer:

• My choice is paper bag and cloth bag. Both are best to use.
• We should not use plastic bags as they are threat to environment.
• Plastic bags are not eco – friendly: They won’t decompose quickly, if you burn them also it will take time to mix with soil.
• Recently in Vijayawada, some areas of the city drowned in rainwater because all the sewage drains were filled with bunches of plastic bags.
• But paper and cloth bags will decompose in very short period and completely eco friendly.
• Paper bags made by wood pulp it may cause deforestation.
• Cloth bags made of cotton, quickly it decomposes.

9th Class Social 7th Lesson Industries in India Important Questions and Answers

Question 1.
Why are the infrastructure facilities important in establishing industries?
Answer:

• Building of roads, good transport facilities, power supply and telephone connections, etc. can be termed as infrastructural facilities.
• Factories need raw materials. These raw materials are to be transported to the factory sites. Hence good road ways and other facilities are needed.
• Factories need power to run machines. Hence all infrastructure facilities are needed.

Question 2.
Why are industries important?
Answer:
In industrial sector, the raw materials are worked upon by people and changed using tools and machines to produce a good that can be useful.
The importance of industries :
i) Industries provide a wide range of products :
There are plenty of goods made in factories. Ranging from paper and other stationery, fridges to cars, batteries, bulbs and other electrical appliances.

ii) Industries are expected to employ a large section of people looking for jobs :

1. Generating employment to work in factories is generally considered as one of the indicators of development and improvement of well being of people.
2. Employment in industries has increased from 11% in 1972-73 to 22% in 2009-10.

iii) Industries are important source of export incomes:

1. We earn a lot of foreign exchange by selling industrial goods to foreign countries.
2. Even today, nearly two-thirds of goods exported is contributed by industries.

Question 3.
What were the restrictions introduced by the government during the early years of industrialization?
Answer:

• Many industrial activities were allowed only for small producers. For example, production of cloth of specific quality was restricted to handlooms.
• Government made laws so that the large factory owners get prior permission or license to set up factories. This was done so that there would be better planning.
• The government regulated the quantity of goods produced by factories.
• The price at which they can be sold was also fixed.

All these restrictions were introduced keeping in view the welfare of the people.

Question 4.
Industrial policies of the early years became hindrance to the growth of industry. Explain.
Answer:

• Entrepreneurs were required to follow so many procedures and had to wait for many years to get the approval from the government offices.
• Licenses were not given to the most efficient producers.
• The selection was biased in favour of people with political connections and the economically powerful.
• All this discouraged new entrepreneurs who would work with latest technology available.
• Further control on prices led to shortage of goods. E.g.: Scooters.
• Such shortages were common for important basic goods like coal and cement, which in turn caused a lot of delay in production of other goods.
• Another problem was lack of quality of some of goods.
• There were restrictions on the import and export of industrial goods including machinery and raw materials.
• Prices were laid down by the government and the producers had to sell only at that price.
  So the above restrictions acted as hindrance to the growth of industry.

Question 5.
Write about the impact of industrial policies.
Answer:
The following are the impacts of industrial policies of government.
i) Rise in the number of industrial units:
Today nearly 2 lakh large factories and 3 crore small factories are operating in India.

ii) Employment has increased but less than expected:
Both small and large scale employ nearly about one-fifth of India’s 460 million workers.

iii) Low salaries and less working conditions:
A large section of workers are employed in small units which generally pay very low salary and devoid of workers safety conditions and health benefits.

iv) Production of factory-based goods has increased:
Establishment of basic industries resulted in increased production of factory based goods.

1. The production of coal and lignite has increased from 32 million tons in 1950-51 to 571 million tons in 2010-11.
2. The production of steel has increased from 10 million tones in 1980-81 to 70 million tons in 2010-11.
3. There was also a significant increase in the production of crude oil and cement etc.

v) Increase in environmental problems, land conflicts and pollution:
These industries release a lot of waste materials into the atmosphere and into the tanks and wells causing lots of air pollution and damaging water resources. The air pollution is causing skin diseases and respiratory diseases.

Question 6.
At the time of independence what were the objectives that were desired to be achieved through industrialization?
Answer:

1. After 1947, India began many initiatives to promote industrial activities in the country.
2. Major objectives were – to become self-sufficient in meeting our needs and to make the country an industrially developed nation.

Question 7.
Where should the sugar and jaggery mills be ideally located?
Answer:
The sugar and jaggery milis should be ideally located near the crop grown areas.

Question 8.
Where would it be economically viable to set up the cement manufacturing units?
Answer:
Cement manufacturing units can be established near the areas where the raw materials are available in bulk.

Raw materials :
Limestone, silica, alumina, gypsum, coal and electric power and transportation facilities.

Question 9.
Name the important centres of cotton textiles in Gujarat.
Answer:
Ahmedabad, Vadodara, Surat, Rajkot and Porbandar.

Question 10.
Where are the silk textile industries located in Jammu and Kashmir?
Answer:
In Baramula, Srinagar and Anantanag.

Question 11.
What are the basic requirements of industrialization?
Answser:

• Industrialization means to develop a large number of different factories.
• For industrialization, we have certain basic requirements.
• They are machines, electricity, minerals and ores and transport facilities.

Question 12.
What factors influence the selection of an industrial location?
Answer:

• Industrial locations are complex in nature.
• These are influenced by raw material labour, capital, power, and market, etc.
• It is rarely possible to find all these factors available at one place.
• So industries are located where these factors even can be arranged at lower cost.

Question 13.
What is an agrobased industry?
Answer:
The industries which are based on agricultural products are called ‘agrobased industries’.

Question 14.
Why do you think cotton textile industry is concentrated in Maharashtra and Gujarat?
Answer:

• Many factors support the concentration of cotton textile industry in Maharashtra and Gujarat.
• Availability of raw cotton, market, transport including accessible port facilities, moist climate etc. are some factors.
• Apart from these, availability of abundunt electricity at cheap prices and availability of skilled and unskilled labour in abundance add to those factors.
• These places also have investment supports from Banks and international market demands.
• Above factors help the flourishing of cotton textile industry in Maharashtra and Gujarat.

Question 15.
Read the following passage and answer the questions given below.

Challenges faced by the industry include stiff competition in the international market from synthetic substitutes and from other competitors like Bangladesh, Brazil, Philippines, Egypt and Thailand. However, the internal demand has been on the increase due to the Government policy of mandatory use of jute packaging. To stimulate demand, the products need to be diversified. In 2005, National Jute Policy was formulated with the objective of increasing production, improving quality, ensuring good prices to the jute farmers and enhancing the yield per hectare. The main markets are U.S.A., Canada, Russia, United Arab Republic, U.K. and Australia. The growing global concern for environment friendly, biodegradable materials, has once again opened the opportunity for jute products.

1) What is the industry mentioned in the above passage?
Answer:
Jute industry.

2) What are the challenges faced by the industry?
Answer:
Challenges faced by the industry include stiff competition in the international market from synthetic substitutes and from other competitors like Bangladesh, Brazil, Philippines, Egypt and Thailand.

3) When was National Jute Policy formulated?
Answer:
In 2005.

4) Name the main markets mentioned in the passage.
Answer:
USA, Canada, Russia, United Arab Republic, UK and Australia.

5) To stimulate demand, the products need to be
Answer:
diversified.

Question 16.
Discuss what is meant by the word “basic”? What are the basic necessities for industries?
Answer:

• “Basic” means the things that are basically necessary.
• The basic necessities for setting up any industries are machines, electricity, minerals and ores and infrastructural facilities like transport, telephone, etc.

Question 17.
Today West Bengal is the dominant state in Jute Industry. How is it able to become like that?
Answer:

• Most Jute mills in India are in West Bengal, mainly along the banks of the Hugli river 98 km long and 3 km wide.
• Hugli basin is in proximity of Jute producing areas, inexpensive water transport, supported by a good network of railways, roadways and waterways to facilitate movement of raw materials to mills.
• Abundant water for processing of raw jute, cheap labour from West Bengal, Bihar, Odisha and Uttar Pradesh.
• Kolkata provides banking, insurance and port facilities for export of jute goods.
• It provides direct or indirect employment to more than 40 lakh people.

Question 18.
Name the problems that are faced in the Iron and Steel industry?
Answer:

• It needs huge capital investment, which is difficult for developing country India.
• Indian technology is now far behind the advanced countries.
• Low per capita productivity and low potential utilization are to be addressed.
• Even at a low per capita consumption, demand for our production is not sufficient.
• Now we are importing iron and steel by spending precious foreign exchange.
• All the above problems needed to be solved.

Question 19.
Locate the following industrial cities on the outline map of India. City

City	Industries Concentrated
Jamshedpur	Iron and Steel company
Ahmedabad	Textile industry
Mumbai	Textile, oil refinery, fertilizers, etc.
Visakhapatnam	BHPV, Steel Plant, Ship building, etc.
Chennai	Cement, Cotton, Railway coaches, etc.
Rourkela	Iron and Steel industry
Kanpur	Leather industry
Madurai	Cotton textile industry
Luduiana	Leather industry
Varanasi	Diesel locomotives

Question 20.
Observe the following map and answer the questions given below.

1) Where do you find both cotton and woollen textiles?
Answer:
In Ahmedabad and Kanpur.

2) What is the South India state famous for silk textiles?
Answer:
Karnataka.

3) Name the important centres of cotton textiles in Gujarat.
Answer:
Ahmedabad, Vadodara, Surat, Rajkot and Porbandar.

4) Which type of textile industries are in major position in Maharashtra?
Answer:
Cotton textile industries.

5) Where are the silk textile industries located in Jammu and Kashmir?
AIn Baramula, Srinagar and Anantanag.

Question 21.
Observe the following map.

Now answer the questions given below.
1) What are the minerals mentioned in the map?
Answer:
Iron ore, manganese, bauxite and mica.

2) In which states do you find iron ore mines?
Answrr:
Maharashtra, Karnataka, Odisha and Chattisgarh.

3) What are the iron ore ex-porting ports mentioned in the map?
Answer:Visakhapatnam, Managalore, Marmagao and Paradwip.

4) Where can we find mica in Andhra Pradesh?
Answer:
In Nellore.

5) What is the mineral found in Rajasthan?
A. Mica.

Question 22.
Observe the following map.

Now answer the questions given below.
1) Which state is Raniganj coal mine located in?
Answer:
West Bengal

2) Where is the coal field located in Tamilnadu?
Answer:
Neyveli

3) Name the important coal mine of Telangana.
Answer:
Singareni

4) What is the coa! field that belongs to Chattisgarh?
Answer:
Korba

Question 23.
What steps are to be taken to reduce the problems of pollution?
Answer:

• We should stop effluent flow into water bodies.
• Provide safety drinking wafer to the affected villages.
• Continuous vigilance in discharge of effluents.
• Medical care to pollution victims.
• Cancellation of licence to pollution causing industries.

Question 24.
What measures would you suggest to overcome the problems of Textile Industry?
Answer:

• Care should be taken to increase the supply of raw material.
• Obsolute machinery which resulting in low productivity and inferior quality should be replaced.
• Government should provide adequate power to textile industry.
• Care should be taken that textile industry shall not lost in the stiff competition with power loom and synthetic fiber products.
• Many textile mills are sick, government should help them run properly.

Question 25.
What suggestions would you make to improve jute industry?
Answer:

• The best way to solve the problems of jute industry is to increase production.
• There is an urgent need to replace the old machinery.
• Jute mills are needed to be modernized.
• New Jute products are to be developed.
• The product range of jute is to be diversified.

AP State Syllabus AP Board 9th Class Social Studies Important Questions Chapter 4 Atmosphere.

AP State Syllabus 9th Class Social Studies Important Questions 4th Lesson Atmosphere

9th Class Social 3rd Lesson Hydrosphere 1 Mark Important Questions and Answers

Question 1.
Why does our skin dry up more during the winter? (SA-II : 2018-19)
Answer:
If the humidity is low in our atmosphere, our skin becomes dry during winter. This also leads to chapped lips.

Question 2.
Define relative humidity. (SA-I : 2019-20)
Answer:
Relative humidity: Relative humidity is the ratio between two things.

1. The maximum water vapour that the air can hold at a given temperature and pressure and
2. The actual amount of water vapour it holds at any given time.

9th Class Social 4th Lesson Atmosphere 4 Marks Important Questions and Answers

Question 1.
How many types of rainfall classified based on the origin of rainfall? What are they? Explain one of them? (SA-II : 2016-17)
Answer:
On the basis of origin, rainfall may be classified into three main types.

1. Convectional Rainfall
2. Orographic Rainfall
3. Cyclonic Rainfall.

Convectional Rainfall :
This type of rainfall occurs when moist air over the heated ground becomes warmer than the surrounding air and is forced to rise, expand, cool and yield some of its moisture.

It is common in low latitudes and on summer days in interior part of the continents, and usually come in the form of short heavy showers just after the hottest part of the day, some times accompanied by thunder and lightning.

Question 2.
Observe the information given below and write four sentences on ‘Pressure Beits and Planetary Winds’. (SA-III : 2016-17)

Answer:
According to the given picture :

• The Equatorial Low Pressure Belts : This low pressure belt extends from 0 to 5° North and South of the Equator.
• Sub – Tropical Pressure Beits : At about 30° North and South of the equator lies the area where the ascending equatorial air currents descends.
• Sub-polar Low Pressure belts : These belts are located between 60° and 70° in both the hemispheres and are known as sub-polar low pressure belts.
• Polar High Pressure belts ; At the North and South between 70° and 90° temperatures are always extremely low. These areas of polar high pressure are known as polar highs.

Planetary winds : Planetary winds are distributed all over the globe and blow in the same direction throughout the year. These winds originate due to the presence of permanent high pressure and low pressure belts on the surface of the earth. The main types of planetary winds are the trade winds, the westerlies and the polar winds.

Question 3.
Study the table and answer the questions given below. (SA-I : 2018-19)

Name of the sphere	Area	Characteristics In equator region
Troposphere	Upto 13 kms.	The entire weather phenomenon happens in this sphere. The temperature in the layer decreases as we go higher.
Stratosphere	Upto 50 kms.	This layer is almost free from clouds and associated weather phenomenon, making conditions most ideal for flying Jet air crafts. One important feature of stratosphere is that contains Ozone layer. The temperature increases with the increase in altitude.
Mesosphere	Upto 80 kms.	Meteorites burn up in this layer on entering from the space. Temperature starts decreasing with the increase in altitude.
Thermosphere	Up to 400 kms.	In thermosphere temperature rises rapidly with increasing height. It contains electrically charged particals known as ions. Radio rays transmitted from the earth by these ions.
Exosphere	Above 400 kms.	It is uppermost layer of the atmosphere. This is the highest layer and very little known about it.

1. Why do jet aircrafts fly in the stratosphere?
2. Which is the top most layer?
3. Which layer contains ions?
4. In which layer does precipitation and cyclones occur?
Answer:

1. Stratosphere layer is almost free from clouds and associated weather phenomenon, making conditions most ideal for flying jet aircrafts.
2. Exosphere. It is above 400 kms. It is uppermost layer of the atmosphere.
3. Thermosphere contains electrically charged particles known as ions.
4. Troposphere.

Question 4.
What are the effects of climate change on the contemporary World? (SA-I : 2018-19)
Answer:
The affect of climate change on contemporary world.
→ an increase in hunger and water crises.
→ health risks through rising air temperatures and heat waves.
→ increasing spread of pests and pathogens
→ loss of biodiversity.
→ melting of the polar caps.
→ El Nino and La-Nino effect.
→ Frequently cyclonic effect on coastal areas, etc.

9th Class Social 4th Lesson Atmosphere Important Questions and Answers

Question 1.
What is Coriolis effect?
Answer:
Because of the impact of Earth’s rotation on its own axis, the winds move slightly to the right in the northern hemisphere, and to the left in the southern hemisphere. This effect is called Coriolis effect.

Question 2.
About which layer do we have very little knowledge?
Answer:
Exosphere is the upper most layer of the atmosphere. This is the highest layer. Very little is known about it.

Question 3.
Why does the amount of water vapour decrease rapidly with altitude?
Answer:
The water vapour is attracted towards the surface or close to the surface due to the gravitational pull of the earth. Hence the amount of water vapour decreases with altitude.

Question 4.
Name and explain the classification of winds.
Depending upon the wind speed, their features, their directions, the way they occur, winds are classified into three types.
A) Planetary winds –
present on the planet as a whole through out the year, that blow continuously and regularly.

B) Seasonal winds –
Restricted to regions or seasonal in character like monsoons.

C) Local winds –
These blow due to local variation in the temperature and pressure, and influence a very small area.

Question 5.
What is a ‘rain shadow’ region?
Answer:

• The moist air is forced to rise over mountain.
• It gives heavy precipitation on the windward side.
• After that the air, which is devoid of moisture blows over leeward side.
• It does not give rain there. So this dry region is known as ‘rain-shadow’ region.

Question 6.
Discuss the cloud formation and various clouds.
Answer:

• Water vapour in the atmosphere attracts dust particles and condense as droplets.
• These droplets in millions and millions together appear like clouds.
• Clouds are different types based on their forms and heights.
• For examples, Cirrus clouds (at higher level), Cumulus clouds (at middle level), Stratus (at lower level) and nimbus (rain bearing and vertical clouds).

Question 7.
How many pressure belts do we have? And what are they?
Answer:
There are seven pressure belts on the earth’s surface. They are :

1. The equatorial low-pressure belt. (1)
2. The sub-tropical high pressure belts. (2)
3. The sub-polar low pressure belts. (2)
4. The polar high pressure belts. (2)

Question 8.
What is relative humidity?
Answer:
The realtive humidity is the ratio between

• The maximum water vapour that the air can hold and
• The actual amount of water vapour it holds.

Question 9.
What are planetary winds? How many types of winds are there?
Answer:
The winds that blow constantly, regularly above the world’s pressure belts are known as planetary winds. They are of three types :

1. Trade winds
2. Westerlies
3. Polar winds.

Question 10.
Write about local winds.
Answer:
The local winds blow due to local variation in the temperature of the area.
These winds are of two types. They are :
1. Hot local winds
2. Cold local winds.

1. Hot local winds :
Hot local winds raise the temperature of the area.

2. Cold local winds :
Cold local winds sometimes bring the temperature of the local area below the freezing points.
Ex : Mistral, Puna, Pampero, etc.

Question 11.
What is NASA?
Answer:
The space agency of USA is NASA, i.e., the National Aeronautics and Space Administration.

Question 12.
“The wind flows from high pressure areas to low pressure areas” – interpret the statement.
Answer:

• When any part of the earth heats up and causes low pressure, it means that there is more vacant space and less molecules.
• Now air from other parts where the pressure is higher moves towards this vacant place.
• It is not difficult for the wind to move along the earth’s surface and thus need not go too much against gravity any more.
• That is why the wind flows from high pressure areas to low pressure areas.

Question 13.
“Heat and pressure – If one increases the other decreases – this is called an inverse relationship” – Interpret the statement.
Answer:

• Due to the heating of the earth’s surface, the gas molecules are heated up, they get a lot of energy and start moving very fast.
• The pressure increases as the molecules will be pushing the object more.
• The energised molecules start flying off higher and higher.
• Now they have more energy to defy the pull of the earth.
• When more molecules go to higher reaches of the atmosphere, the place near the earth has less molecules, this means less pushing around or less pressure.
• Thus when it gets hot, the air pressure becomes low and when it becomes cool, the pressure increases.
• In simpler terms “If one increases the other decreases”-this is called an inverse relationship.

Question 14.
Nowadays there is great demand for energy. Conventional energy sources are depleting quickly. In the light of this, assess wind as alternate energy?
Answer:

• Nowadays there is great demand for energy and conventional energy sources are depleting quickly.
• In these situation wind energy is definitely an alternate energy source.
• Winds like planetary, which blow constantly and regularly are of great help in energy production.
• Wind energy is not an exhausting one like conventional resources.
• Winds of other nature like monsoon and local winds also come handy in energy production.

Question 15.
Observe the figure and answer the questions that follow.

1. To which pressure belts are the westerlies blowing?
Answer:
The westerlies are blowing towards sub-polar low pressure belts.

2. To which pressure belts are the easterlies blowing?
Answer:
The easterlies are blowingtowards sub-polar low pressure belts.

3. What are the winds that are blowing towards the equatorial Sow pressure belts?
Answer:
Trade winds are blowing towards the equatorial low pressure belts.

4. What is the other name for the equatorial low pressure belts?
Answer:
The equatorial low pressure belts are also known as “the equatorial doldrums” or ITCZ i.e., Inter-Tropical Convergence Zone.

5. Towards which direction (right or left) are the planetary winds blowing?
Answer:
The winds in the Northern hemisphere are deflecting towards right and the winds in the southern hemisphere are deflecting towards left due to coriolis effect.

Question 16.
Appreciate the role of winds in weather and climate patterns. Draw a parallel from history.
Answer:

• Winds play a very important role in the weather and climate patterns around the world.
• They have also played a very important role in history.
• For example, Vasco da Gama found sea route to India using winds to power his ships.
• He was able to transport and trade in spices with help of these winds.
• These winds are crucial for Portugese to rule over Goa.

Question 17.
Explain the measures to be taken to mitigate the cyclones.
Answer:

• Early warning systems are needed to be installed by the government.
• Government should inform people in advance about the possibility of disasters like cyclones.
• Government shall provide people with longterm security like strong roads, safe pucca houses for people of low land areas.
• Food, water and medical emergency teams should be kept ready whenever there is a forecast of cyclone.
• Close cooperation between people, Non-Governmental organizations and Government organizations are essential to mitigate cyclone affects.

SCERT AP Board 9th Class Social Solutions 24th Lesson Traffic Education Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 24th Traffic Education

9th Class Social Studies 24th Lesson Traffic Education Textbook Questions and Answers

Improve Your Learning

Question 1.
What documents should a driver carry while driving and what skills are needed to drive safely?
Answer:
The following documents should be carried while driving :

1. Driving license
2. Registration certificate
3. Taxation certificate
4. P.U.C. certificate
5. Insurance certificate
6. Fitness certificate and permit

The following is a basic description of the skills and abilities a driver needs before getting in the driver’s seat. This applies to people of all ages.

Physical skills and abilities :
Driving requires physical strength. It takes a lot of muscle work too.

1. Hold the body upright to use and control the steering wheel,
2. Maintain sitting balance,
3. Control the head, neck, arms and legs, feet and hands.
4. To operate a vehicle

Physical and mental stamina and muscle flexibility are needed to :

1. sit and drive
2. focus constantly on the task of driving.
3. twist and turn
4. move the head and’ neck side to side, up and down, back and forth.

In addition to these driving requires a clear and alert mind.

Question 2.
What will happen if someone jumps the traffic signal?
Answer:
Traffic signals help to control traffic. It someone jumps the traffic signal, there is a chance of accident.

Question 3.
Suggest a few steps that are taken in your area for road safety.
Answer:
Road safety is a result of contributing efforts from all the sections the society including both civilians and government officials. In addition to the human sufferings, the estimated costs of the road injuries are a noticeable amount in GNP per annum. So some steps can be fruitful in this direction.
A few important road safety steps :

1. Don’t use mobile phone whilst driving.
2. Belt up in the back.
3. Don’t drink and drive.
4. Always adhere to speed limits.
5. Take special care about children, senior citizens and pedestrians.
6. Don’t drive if tired.
7. Pedestrians should walk cautiously.
8. Always observe and anticipate other road users.
9. Keep your distance and
10. Always wear helmets and seat belts.

We follow all these road safety rules in our area.

Question 4.
Explain mandatory, caution and information traffic signs with examples.
Answer:
1) Mandatory signs :
Mandatory signs are indicated in a circular form. In accordance with the motor vehicle Act 1988, every driver of a motor vehicle shall drive the vehicle in conformity with any indication given by the mandatory signs and not obeying there signs is an offence.
Ex : 1. Stop
2. No Parking
3. Overtaking prohibited

2) Cautionary /Warning signs :
Cautionary signs are meant for cautioning the driver about the hazards lying ahead on the road. Drivers must obey there signs for safety. These signs are indicated in a triangular form
Ex : 1. T -inter section
2. Right hand curve
3. School ahead

3) Information signs:
Informatory signs are erected on the road to provide information on direction, destination, road side facilities etc., to the road users.
Ex : 1. Park this side
2. First aid post
3. Public telephone

Question 5.
Kamala wants to purchase a new vehicle. Explain her what are the steps to be taken and what documents are to be produced for the registration of a vehicle?
Answer:
The steps to be taken by Kamala in purchasing a car or something else :

1. Starting out
2. Using incentives and rebates
3. Pricing the car
4. Finding the exact car you want to buy
5. Test driving the car salesman
6. If you are trading in your old car
7. Negotiating for the best finance options
8. Closing the deal
9. Reviewing and signing the paper work,
10. Inspecting and taking possession of your new car.

Documents to be produced for the registration of a vehicle :

1. R.T.O. forms – a) Form 20 b) Form 34
2. Pan card , copy of sales certificate
3. Address proof
4. Insurance cover note
5. Person’s authorized signature
6. Copy of road worthiness certificate
7. Pollution under control certificate

Question 6.
Ramu wants to interchange his vehicle number to other vehicle. Is it correct or not?
Explain, why.
Answer:
No. Ramu cannot interchange his vehicle number to other vehicle.
Reason : Any vehicle registered for its particular registration mark will remain its
identifications and interchange of it is not allowed.

Question 7.
Explain the need of road safety.
Answer:
India loses more than 1,00,000 lives due to road traffic crashes every year. It has a road traffic fatality rate of 16.8 deaths per, 1,00,000 population. Approximately half of all deaths on the country’s roads are among vulnerable road users – motorcyclists, pedestrians and cyclists.

Hence road safety is very important to avoid the accidents and control loss of lives. Road safety ensures that every road user follow traffic rules and thereby avoid traffic jams and deaths due to accidents. For systematic regulation of vehicular traffic, road safety is needed.

Question 8.
Read the table of page ‘Accident Victims Age’ on page 286, identify the age group for which more number of cases registered and draw a bar graph.

Age	Cases	Age	Cases
00-05	24	50-55	207
05-10	58	55-60	138
10-15	40	60-65	113
15-20	152	65-70	57
20-25	345	70-75	49
25-30	380	75-80	13
30-35	254	80-85	12
35-40	294	85-90	0
40-45	226	90-95	0
45-50	215	95-100	0

Answer:
More number of cases registered age group 35 – 40 years age group.

Question 9.
Read the paras under the title ‘Traffic Chaos’ of page 287 and comment on them.
Traffic Chaos:
You have to go to school on the morning. If you are late, you may miss classes. You are struck in a traffic jam. What will you do?
Students, employees, labourers, teachers, doctors and all are affected by traffic jams. Foot paths (Side walks) are considered a boon for pedestrains. Sometimes motorists drive on these side walks also.

Stray animals, fruit and vegetable seller, private vehicles like cars, autorickshaws are parking at No Parking Zones are the main causes for traffic jams. As there is an increase in population and use of automobiles, there has been a rapid increase in the volume of traffic on roads. To avoid the accidents, one must know the prescribed rules and regulations.
Answer:

Road sense on Indian streets is often completely missing. The Indian traffic conditions are chaotic, the drivers are reckless, and the roads are poor repair conditions.

There is a pecking order for right of way – cows / buffaloes are at the top, trucks and buses are second, and dogs and pedestrians are at the bottom. Two wheelers are pretty low down. Pot holes and speed breaker bends are common and rarely marked. Pedestrians, . animals, bicycles, ox carts and tractors all use the roads.

Question 10.
Collect the data from the traffic police /RTA officials who are nearest to you.
Month : Place :
No. of cases booked :

Analyse the data and discuss in your classroom regarding traffic situations in your area.
Answer:
Month : September Place : Vijayawada
No. of cases booked : 1986

The above data is revealing us the negligence of the vehicle riders and road users. They are to be strictly punished.

9th Class Social Studies 24th Lesson Traffic Education InText Questions and Answers

Question 1.
Why is it compulsory to have a driving license? (Text Book Page No. 288)
Answer:
Yes, it is compulsory to have a driving license. As per Motor Vehicle Act 1988, a valid driving license is necessary to drive any motor vehicle on public roads.

Question 2.
Observe the given table and answer the questions. (Text Book Page No. 286)

Age	Cases	Age	Cases
00-05	24	50-55	207
05-10	58	55-60	138
10-15	40	60-65	113
15-20	152	65-70	57
20-25	345	70-75	49
25-30	380	75-80	13
30-35	254	80-85	12
35-40	294	85-90	0
40-45	226	90-95	0
45-50	215	95-100	0

1) In which group do you find more cases? Can you say, why.
Answer:
25 – 30. As the people in this age become more independent, they are exposed to risks.

2) How many cases are there in the age group of both 20 – 25 and 25 – 30?
Answer:
345; 380

Question 3.
Observe the following pie-chart and answer the following questions. (Text Book Page No. 287)
1) Discuss the data relating to the accidents – accused vehicles in your classroom.

Answer:
Group discussion in classroom

2) Which type of vehicles are accused of more accidents? Can say why?
Answeer:
Two wheelers. Because they are in more number.

3) What are Traffic Rules and regulations? Discuss in your classroom.
Answer:
Traffic rules and regulations of the road are both the laws and the informal rules that may have been developed to facilitate the orderly and timely flow of traffic.
Note : Students should discuss in the classroom.

Question 4.
With the help of your teacher collect the road surface markings from RTA/Traffic police and discuss the uses of various markings in the classroom. (Text Book Page No. 290)
Answer:
Uses of various markings :

1. Road surface markings are used on paved roadways to provide guidance and information to drivers and pedestrians.
2. These markings promote road safety.
3. These are used to supplement the message of road signs and other devices.

Note : Students should collect road surface markings and discuss in the classroom.

SCERT AP Board 9th Class Social Solutions 17th Lesson Colonialism in Latin America, Asia and Africa Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 17th Colonialism in Latin America, Asia, and Africa

9th Class Social Studies 17th Lesson Colonialism in Latin America, Asia and Africa Textbook Questions and Answers

Improve Your Learning

Question 1.
Match the following :

Group – A	Group – B
1. Opium war	A) Belgium
2. Ottoman empire	B) Spain
3. Personally owned the	C) Controlled trade before colonization
4. Setting farmers	D) China

Answer:

Group – A	Group – B
1. Opium war	D) China
2. Ottoman empire	C) Controlled trade before colonization
3. Personally owned the	A) Belgium
4. Setting farmers	B) Spain

Question 2.
How is the word ‘discovery’ and ‘exploration’ used by Europeans? What did it mean to people who were already living in those geographical locations?
Answer:
Discovery:

• The word “discovery” means “finding something that we did not know about it before”.
• But in European concept “discovery” is to find faster and easier routes to countries like India, China etc., without passing through regions controlled by Italian traders.

Exploration :

• The step next to discovery is exploration.
• Exploration in European context means “Sending expedition to countries and finding out what resources were available.”
• Europeans explored the backward African and Asian countries for natural resources like, gold, silver, silk, porcelain etc.

Views of native people :

• But the Europeans did not explore these countries but exploited them.
• Virtually the Europeans enslaved them, plundered them, forced them to trade with them etc.
• In South America the natives were deprived of their land and were massacred and driven to interiors.

Question 3.
What role did trade play in the colonisation?
(OR)
“Trade played a major role in the colonisation.” Do you agree? Why?
Answer:
Yes. I agree with this statement.
Reasons:

• Trade played an important role in colonizations.
• Trading items include silk, porcelain, tea, etc., from China; cotton textiles, steel and spices from India; tin, petroleum, rubber, spices, etc., from Indonesia and natural resources from Africa.
• The Europeans had established trading centres in these countries.
• They demanded monopolistic trade relations for the benefit of the colonial powers.
• The European powers had bought these exotic goods and sold them in Europe and made high profits.
• The first Dutch expedition, for example, fetched about 400% profit on its investment.
• As much of 25% of the Dutch government budget came from these profits.
• The English people forced Indians to produce opium and sold that opium in China and earned heavy profits.
• Thus trade played an important role in colonization.

Question 4.
How did the lives of native people in different countries affect the colonisation? Write two ideas each in the context of – crops cultivated/religion/use of natural resources – for the three continents.
Answer:

• Most of the countries were self-sufficient before colonization.
• These colonies were impoverished during colonial powers.

Crops cultivated :

• They were cultivating food crops and the colonies in all three continents were forced to cultivate commercial crops.
• There were shortage of food items and famines and droughts were frequent.

Religion :

• In Asia people were Hindus, Muslims and Buddhists. In Indonesia Muslims were massacred and forced to convert into Roman Catholism.
• In other continents also the Catholic Church played important role in the governance of the colonies.

Use of natural resources :

• All the natural resources like gold, diamonds, silver, iron, coal, tin, rubber, silk, copper were plundered and taken into their countries.
• Colonial powers developed industries in their countries with these resources.

Question 5.
Compare the nature of colonial rule over China and India and Indonesia. What difference and similarities do you find between them?
Answer:

Question 6.
Locate the Portuguese, Dutch, British and French colonies in the world map and filled with different colours.
Answer:

Question 7.
If you were a citizen of Britain, could you support its colonisation? As an Indian citizen could you support or reject colonisation. Give a brief account of your views.
Answer:
Attitudes towards colonialism have varied greatly from time to time and from place to place. I think this is ever present truth that the strong dominate the weak.

If I were a citizen of Britian or as Indian I strongly oppose this colonisation. Because every living being in this world has the freedom in the world. So I don’t like to arrest the others’ freedom.

9th Class Social Studies 17th Lesson Colonialism in Latin America, Asia and Africa InText Questions and Answers

Question 1.
Which of the continents were they not familiar with at all? (Text Book Page No. 205)
Answer:
The Europeans were not familiar with the continents of South America and North America.

Question 2.
Which were the continents whose coastal areas were known to them but not the interior regions? (Text Book Page No. 205)
Answer:

• The coastal areas of Africa were known to the Europeans.
• They established trade relations with Asian countries during ancient and medieval periods. Hence the coastal areas of Asia were also known to them.

Question 3.
Why do you think the Spanish Settlers were not allowed positions of importance in the government of the colonies? (Text Book Page No. 208)
Answer:

• Even though the direct colonial rule ended, many remains of the old colonial rule remained.
• Latin Americas had a social system which consisted of very large landlords, a large number of slaves, semi slaves and poor small farmers.
• Industry and trade were under the control of the landlords.
• These landlords paid no interest in developing.
• Old colonialism continued to influence the Latin Americas even after the end of the colonial regime.

Question 4.
Compare the Zamindari system in the Nizam state and the haciendas of South America. What similarities and differences do you find between them? (Text Book Page No. 209)
Answer:

• Haciendas were estates of thousands of acres which contained silver and copper mines, agricultural lands and also factories. They were owned by landlords.
• “Zamindari System” was created by the government. Zamindars were appointed and they were made the owners of the lands. Original owners became tenants.
• Landlords used to employ peons or unfree Indians and African slaves to work on Haciendas.
• Tenents used to work on the lands in Zamindari system and taxes were collected by the Zamindars.

Question 5.
Why do you think the Latin American countries remained undeveloped despite getting independence from colonial rule? (Text Book Page No. 211)
Answer:
I think that the Latin American countries remained undeveloped despite getting independence form colonial rule due to the following reasons :

1. Poverty,
2. Corruption,
3. Lack of a manufacturing base,
4. Drugs,
5. Poor leadership and
6. The U.S.A.

Question 6.
In what way did the Munroe doctrine protect the independence of Latin America? Did it also limit their freedom? (Text Book Page No. 211)
Answer:

• The Munroe doctrine had no clarity regarding the independence of Latin America.
• It asserts that European powers should not consider colonising any American country but it allows an American country to colonize these countries.

Question 7.
How did Britain gain from the Munroe Doctrine? (Text Book Page No. 211)
Answer:

• Britain which had a powerful navy supported the Munroe Doctrine.
• Britain was keen that the American colonies were not under political control of any European power so that they would be free to trade with England and purchase its industrial goods.

Question 8.
Fill in the blanks : (Text Book Page No. 215)
a) Main products imported by western countries from China were ………………………….. and ………………………….. .
b) The product that western countries tried to sell in China was …………………………..
c) Asian country that tried to influence trade in China was …………………………..
Answer:
a) silk, porcelain and tea
b) opium
c) Japan

Question 9.
Read the following passage and answer the questions given below.

Most of the trade routes connecting Europe and Asia around 1400 were controlled by Muslim kingdoms, especially the Ottoman Empire which was constantly at war with the European Christian powers. The Italians were able to work out an understanding with the Arab traders who brought Asian goods to the Alexandria (in Egypt) and sold them to the Italians. As traders and governments of western Europe like Holland, Spain, Portugal and England realised the importance of this trade, they wanted to find faster and easier routes to countries like India and China, without passing through regions controlled by Italian traders. The Portugese for example, wanted to find a route around Africa to reach India. The Spanish wanted to know if it was possible to reach India by crossing the Atlantic Ocean. They invested huge fortunes by hiring experienced sea mariners and giving them ships and other resources to explore. This led to the discovery of Central America by Christopher Columbus in 1492 and of sea route to India around Africa by Vasco Da Gama in 1498. Columbus was working on behalf of the Spanish queen while Vasco da Gama was working for the Portugese king. Soon English and Dutch governments too were sending their sailors to these regions.

a) Why do you think the Italians were controlling the trade with Asia in 1400 and not other Europeans like Portuguese or Spanish? (Text Book Page No. 206)
Answer:

• As per theory the Italians came to an understanding with the Arab trader who brought Asian goods to the Alexandria and sold them to the Italians.
• But in reality Italy is in the Mediterranean sea and is very accessible to Egypt, Middle east and east Asian countries. Hence developed good trade with them.

b) Why were the Portuguese and Spanish keen to find other routes to reach Asia? (Text Book Page No. 206)
Answer:

• Italy developed due to the Asian trade.
• So other countries realised the importance of this trade.
• They wanted to find faster and easier routes to countries like India and China without passing through regions controlled by Italian traders.

Question 10.
Look at the map of South America around 1800 to identify the countries controlled by the different powers. (Text Book Page No. 202)

Answer:
Student activity.

Question 11.
Try to formulate the grievances of the following people of the Latin American colonies. (Text Book Page No. 209)
1) Spanish settlers who owned haciendas
2) Small Spanish farmers settled in America
3) Native Americans
4) African slaves settled in Latin America.
Answer:

1.  a) Haciendas were estates of thousands of acres.
   b) These estate owners had no intensives to use modern methods of cultivation or production as they had a supply of cheap abour.
2. Small Spanish farmers did not have any role in the administration of the colonies which were controlled by the Spanish from Europe.
3. A large number of native Americans had been killed. The survied were heavily taxed, and had to provide labour supply to the mines and farms owned by the Spanish.
4. Most of the African slaves were forced to work on the haciendas.

Question 12.
Look at the Map of Africa in 1913 to see the extent of colonial possessions of the European powers in Africa.
Compare the map with a modern map of Africa.
Make a list of the large African countries and write against their names the countries that had colonised them. (Text Book Page No. 216)

(OR)
Look at the two maps given beiow Map A shows the European colonies in Africa in 1913-14 and Map B shows the modern countries of Africa.

Compare the information in this two maps. Draw the table given below in yours answer sheet and write the name of the colonising country against the African Country given.
Answer:

Modern country	Colonial power in 1913
1. South Africa	Britain
2. Egypt	Britain
3. Nigeria	Britain
4. Ghana	Britain
5. Libya	Italy
6. Algeria	Italy
7. Angola	Portuguese
8. Congo	Belgium (Later it became French colony)

 

AP State Syllabus AP Board 9th Class Physical Science Solutions Chapter 7 Reflection of Light at Curved Surfaces Textbook Questions and Answers.

AP State Syllabus 9th Class Physical Science Solutions 7th Lesson Reflection of Light at Curved Surfaces

9th Class Physical Science 7th Lesson Reflection of Light at Curved Surfaces Textbook Questions and Answers

Improve Your Learning

Question 1.
“Laws of reflection of light are not applicable to curved surfaces” Is it correct?
Answer:
No, laws of reflection of light are applicable to curved surfaces also.

Question 2.
How do you find the focal length of a concave mirror?
(OR)
What is the name given to distance between pole and focal point? How would you able to find that distance by using an activity? That distance is called focal length.
Answer:

To find the focal length of a concave mirror –

1. Hold a concave mirror perpendicular to the direction of sunlight.
   Take a small paper and slowly move it in front of the mirror and find out the point where you get smallest and brightest spot, which is image of the sun.
   The rays coming from sun parallel to the concave mirror are converging at a point.
   This point is called Focus or focal point (F) of the concave mirror.
   Measure the distance of the spot from the vertex (point P) of the mirror.
   This distance gives the focal length of the concave mirror.

Question 3.
Where will the image form when we place an object, on the principal axis of a concave mirror at a point between focus and centre of curvature?
Answer:

• When we place an object on the principal axis of a concave mirror at a point between focus and centre of curvature then the image will form at a point beyond the centre of curvature.
• The image is enlarged, inverted and real.

Question 4.
Find the distance of the image, when an object is placed on the principal axis at a distance of 10 cm in front of a concave mirror whose radius of curvature is 8 cm.
(OR)
If the object is placed on the principal axis at a distance of 10 cm in front of a concave mirror with curvature is 8 cm, what is the distance of the image?
Answer:
Object distance u = – 10 cm
Radius of curvature (R) = – 8 cm
∴ Focal length f = \(\frac{R}{2}=\frac{-8}{2}\) = – 4 cm
Image distance = v = ?

∴ The image distance = 6.67 cm.
i.e., Real image is formed at same side of the mirror.

Question 5.
State the differences between convex and concave mirrors.
(OR)
Distinguish between convex and concave mirrors.
(OR)
Ramu observed a mirror which is used by drivers to see the vehicles behind. Srinu observed a mirror which is used by dentist to see teeth inside the mouth. What are those two mirrors and distinguish them?
Answer:
Those mirrors are (1) Convex, (2) Concave

Convex mirror	Concave mirror
1. After reflection from the mirror the light rays diverge.	1. After reflection from the mirror the light rays converge.
2. The reflecting surface curved outward.	2. The reflecting surface curved inward.
3. Radius of curvature and focal length are taken as positive, in sign conversion.	3. Radius of curvature and focal length are taken as negative, in sign conversion.
4. It’s magnification is positive only.	4. It’s magnification may be both positive and negative.
5. Magnification of convex mirror is in between zero and one.	5. Magnification value of concave mirror having all values.
6. The image formed due to convex mirror is always virtual.	6. The image formed due to concave mirror is generally real. But when an object placed between vertex and focus it is virtual.
7. The image formed due to convex mirror is always diminished.	7. The image formed due to concave mirror is diminished or magnified or same size based on position of object.
8. The image due to convex mirror is always erect.	8. Generally the image is inverted except when the object is placed between P and F.

Question 6.
Distinguish between real and virtual images.
(OR)
Varun sees his image in a concave mirror. When he moves away he was unable to see his image. Write the differences between those two images.
Answer:

Real image	Virtual image
1. Real image is formed due to converging of light rays.	1. Virtual image is formed due to diverging of light rays.
2. This image can be formed on screen.	2. This image cannot be formed on screen.
3. Generally this image is inverted.	3. Generally this image is erect.
4. It cannot be seen in the mirror.	4. It can be seen in the mirror.

Question 7.
How do you get a virtual image using a concave mirror?
(OR)
Ramu moved an object towards a concave mirror. When he reached certain point he was able to see his image. Where does he had placed the object inorder to see the object in the mirror?
Answer:

• Place the object at a distance less than the focal length of the mirror.
• Draw ray diagram as shown in the figure.
• When the rays are extended, they seem to be coming out from a point on the other side of the mirror. (G)
• We cannot find the image on the screen, but we can see the image in the mirror. (IG)
• This is the virtual, erect and magnified image.

Question 8.
What do you know about the terms given below related to the spherical mirrors?
a) Pole
b) Centre of curvature
c) Focus
d) Radius of curvature
e) Focal length
f) Principal axis
g) Object distance
h) Image distance
i) Magnification
Answer:
a) Pole :
The centre of the spherical mirror is called pole of the mirror.

b) Centre of curvature :
The normal from a concave mirror converge at a point, that point is called centre of curvature.

c) Focus :
A point on the principal axis where a beam of light parallel to the principal axis either converges into or appears to diverge from after reflection from the mirror is called focus (or) focal point (F).

d) Radius of curvature :
The distance between pole and centre of curvature is called radius of curvature. It is denoted by ‘R’.
R = 2f

e) Focal length :
The distance of the focus from the pole is called the focal length (f) of the mirror.

f) Principal axis :
The horizontal line which passes through the centre of curvature and pole.

g) Object distance :
The distance between object and mirror is called object distance (u).

h) Image distance :
The distance between image and mirror is called image distance (v).

i) Magnification :
The ratio of size of image to the size of object is known as magnification.

Question 9.
Write the rules for sign convention.
(OR)
Vinay wants to solve a problem related to mirrors. What are rules to be followed by him in order to solve the problem?
Answer:

Sign conventions used in mirror equation :

1. All distances should be measured from the pole.
2. All distances measured in the direction of incident ray are to be taken as positive.
3. The distances measured in the direction opposite to incident ray are to be taken as negative.
4. Height of object (h₀) and height of image (h_i) are positive, if measured above principal axis and negative if measured below principal axis.

Question 10.
The magnification produced by a convex mirror is – 1. Do you agree it?
Answer:
The magnification produced by a convex mirror is – 1.1 agree with this statement.

Question 11.
Imagine that spherical mirrors were not known to human beings. Guess the consequences.
(OR)
What are the consequences occur when the spherical mirrors were not known to human beings?
Answer:

• Spherical mirrors are used by human beings in their daily life.
• Convex mirrors are used in hospitals, hotels, stores, apartments, roads, ATMs, computer monitors, rare-view mirrors in vehicles, and also in sun glasses,
• Whereas concave mirrors are used by ENT specialists, dentists to see inner parts of mouth,
• Car head lights are used to get parallel beam of light,
• Solar cookers are also made from concave mirrors, So everywhere we are using these spherical mirrors,
• So without these spherical mirrors the life of human beings is miserable,

Question 12.
By observing steel vessels and different images in them, Surya, a third class student, asked his elder sister Vidya some questions. What may be those questions?
(OR)
By observing the image on steel vessels, Surya asked his sister some questions. What may be those questions?
Answer:

• Why do we see our image in some vessels which bulged outwards?
• Why are we not able to see our image in some vessels which bulged inwards?
• Which type of vessels are useful to reflect light on wall and form our image on wall?
• Can we see the images in all vessels?
• Is these images real or virtual?
• The vessels which are bulged inside behaves like which type of mirrors?

Question 13.
How do you form a diminished image by a concave mirror on a screen?
Answer:
If we place an object beyond centre of curvature of a concave mirror, diminished image will be formed between focus and centre of curvature,

Question 14.
How do you find the focal length of a concave mirror in the lab?
Answer:
Aim :
To find out focal length of a concave mirror,

Material required :
A candle, paper, concave mirror, V-stand, measuring tape, or meter scale.

Procedure:
1) Place the concave mirror on V-stand, a candle, and meter scale as shown in figure.

2) Keep the candle at different distances from the mirror (10 cm to 80 cm) along the axis and by moving the paper (screen) find the position where you get the sharp image on paper.

3) Note the distance of candle from the mirror (u) and distance of the image from the mirror (v) in the given table.
Here u = object distance, v = image distance, f = focal length.

4) Find the average of T. This value of T is the focal length of the given concave mirror.

Question 15.
What do you infer from the experiment which you did with concave mirrors and measured the distance of object and distance of image?
Answer:
I observed the following points from the experiment with concave mirrors, to form images at different places, they are :

1. As the object distance increases, the image distance decreases.
2. As the object distance increases, the size of image decreases.

Question 16.
Draw a ray diagram to show the process of converging of the parallel beam by a concave mirror by taking four parallel incident rays.
Answer:

Question 17.
Draw suitable rays by which we can guess the position of the image formed by a concave mirror.
Answer:
Suitable rays by which we can guess the position of the image formed by a concave mirror.

Rule 1 :
All the rays, that are parallel to the axis, get reflected such that they pass through the focal point of the mirror.

Rule 2 :
A ray that passes through the focal point of the mirror will, travel parallel to the axis after reflection.

Rule 3 :
A ray, passing through the centre of curvature of the mirror and incidents on the mirror, after reflection will travel along the same line, but in opposition direction.

Question 18.
Show the formation of image with a ray diagram, when an object is placed on the •principal axis of a concave mirror away from the centre of curvature.
Answer:

Question 19.
Make a solar heater / cooker and explain the process of making.
(OR)
Which cooker uses solar energy to cook food and explain its making?
(OR)
Explain the construction and working of a solar cooker.
Answer:

Construction:

1. Make a wooden / iron frame in dish shape. It is solar cooker.
2. Cut the acrylic mirror sheets into 8 or 12 pieces in the shape of isosceles triangles with a height equal to the radius of a dish antenna.
3. The bases of 8 or 12 triangles together make the circumference of the dish.
4. Stick the triangle mirrors to the dish as shown in figure.
5. Thus solar heater/cooker is ready.

Working:

1. Face it towards the sun.
2. Find its focal point and place a vessel at that point.
3. It will get heated. Everyone cook rice in that vessel.

Question 20.
To form the image on the object itself, how should we place the object in front of a concave mirror? Explain with a ray diagram.
(OR)
Draw ray diagram to explain the image formation on the concave mirror if the object is in front of it.
Answer:

• The object should be placed on centre of curvature of concave mirror.
• When the object placed at centre of curva¬ture after reflection from the mirror the light rays converge at centre of curvature.
• So a real and inverted image is formed on the object itself. Ray diagram

Question 21.
How do you appreciate the role of spherical mirrors in our daily life?
(OR)
Write the usage of spherical mirror in daily life situations.
Answer:

• Spherical mirrors are useful in our daily life in many ways.
• Convex mirrors are used as rear view mirrors in cars, scooters, buses, etc. This helps us to see the traffic behind the vehicle, which avoids accidents while taking turns.
• Big convex mirrors are used as shop security mirrors.
• Concave mirrors are used by dentists, opthamologists, to see the smaller parts of teeth, eyes, and ears.
• Concave mirrors are also used in solar heating devices.
• Concave mirrors are used as shaving mirrors to see a large image of the chin (or) face.
• Concave mirrors are used as doctor’s head mirrors to focus light coming from a lamp on to the body parts of the patient to be examined by the doctor.
• So, I appreciate the role of spherical mirrors in our daily life.

Question 22.
How do doctors use concave mirrors?
Answer:

• Dentists and ENT specialist doctors use concave mirrors to get a magnified clearer view of the teeth, skin and ear cavities.
• A concave mirror converges the rays of light falling on it in a direction parallel to the principal axis, on to its focus. This is the reason why ENT specialists use it as a head mirror.

Question 23.
Why do we prefer a convex mirror as a rear-view mirror in the vehicles?
Answer:

• Convex mirror always gives an erect and diminished image.
• The image distance will be smaller than the object distance.
• A convex mirror has a wider field of view than a plane mirror.
• Hence we prefer convex mirror as rear-view mirror in the vehicles, as we have to observe the vehicles which are at the back of our vehicle.

Question 24.
Complete the table-1 which is related to experiment done by a concave mirror.

Object distance	Image distance	Magnification
1. 10 cm
2. 20 cm
3. 30 cm
4.	40 cm	1

Answer:

Object distance	Image distance	Magnification
1. 10 cm	20 cm	2
2. 20 cm	Infinity	Cannot measure
3. 30 cm	60 cm	2
4. 40 cm	40 cm	1

From the given data, m = \(\frac{40 \mathrm{~cm}}{40 \mathrm{~cm}}\) cm = 1.
Hence, R = 40 cm, f = 20 cm.

Question 25.
How can you show the diverging and the converging of light by using laser lights?
Answer:
Aim :
To show diverging and converging of light by using laser lights.

Material required :
Concave mirror, convex mirror, laser lights-2, screen, V-stand, Agarbathi.

Procedure:

• Place a concave mirror on a V-stand and place the V-stand on a table.
• Take two laser lights.
• Focus the light rays of laser lights parallel to the axis of the concave mirror.
• The light rays (beams) incident on the concave mirror are reflected back and converge at one point.
• Place the screen to catch that converging point of reflected light rays.
• Light a Agarbathi near the table.

Observation :
We can observe path of the incident and reflected rays clearly in the smoke of Agarbathi.

• Now place a convex mirror on the stand.
• Again pass the laser light rays parallel to the principal axis at the convex mirror.

Observation :
We can observe diverging light rays. We cannot catch any converging point on the screen.

Question 26.
Collect information about the history of spherical mirrors in human civilization. Display it in your classroom.
Answer:

• The idea of mirror came into existence long back when people saw their images in water, on poluted surfaces, etc.
• The history of mirrors starts in the 6000 BC. The earliest man made mirrors were pieces of poluted stone.
• The first glass mirrors were produced in 1A.D. by Romans.
• The first modern silver-glass mirror was created by Justus Von Liebig, a German chemist in 1835.
• The invention of glass blowing method during the 14th century led to the discovery of spherical mirrors, which increased the popularity of glass mirrors.
• By the end of 18^th century, decorative mirrors have widely used.
• New, cheaper techniques of mirror production in the 19th century led to a great proliferation in their use.

Question 3.
Think about the objects which act as a concave or convex mirrors in your surroundings. Make a table and display it in your classroom.
(OR)
Collect some objects from your surroundings that act as concave, convex mirrors and display them your classroom.
Answer:
Object used as convex and concave mirror in our surroundings.

Convex mirror	Concave mirror
1. Spoon bulged outwards.	1. Spoon bulged inwards.
2. Outer surface of cooking vessel.	2. Inner surface of cooking vessel.
3. Sink outwards.	3. Sink (wash basin) inwards.
4. Glass outwards.	4. Glass inwards.

Question 4.
How will our image be in concave and convex mirrors? Collect photographs and display in your classroom.
Answer:

• In concave mirrors our image is thin and enlarged.
• As we move away from mirror the image will be diminished and become pointed at the pole.
• In convex mirror, our image is bulged and size of image is diminished.
• As we move away from the mirror, the image is further diminished.

Question 5.
How do you appreciate the use of reflection of light by a concave mirror in making of TV antenna dishes?
Answer:

• The parabolic shape of dish reflects the signals to the dish’s focal point.
• Mounted on brackets at the dish’s focal point is a device called a feed horn.
• This feed horn is a wave guide that gathers the signals at or near the focal point and conducts them to a LNB (Low-Noise Block down converter).
• The LNB converts these electromagnetic waves into electrical signals and shifts to the receiver i.e. T.V. set.
• This is all possible only with the help of parabolic dish antennas (concave shape).
• We know, the T.V. plays an important role in our daily life. So the inventions of the utilities of concave shapes are more helpful for us.

Question 6.
A convex mirror with a radius of curvature of 3 m is used as rear view in an automobile. If a bus is located at 5 m from this mirror, And the position, nature and size of the image.
Answer:

Position = 1.15 m behind the mirror. Nature = Virtual and erected.
∴ Image is erect and smaller in size by a factor of 0.23.

Question 7.
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
(OR)
An object 5 cm high is placed at a distance of 10 cm from a convex mirror, the focal length of the mirror is 15 cm. Find the nature, position and size of the image.
(v = +6m ; m = 0.6, h₂ = 3 cm)
Answer:
Given, u = – 10 cm ; f = 15 cm ; v =?

So the Image is virtual and seen in the mirror.
Magnification m = \(-\frac{v}{u}=\frac{-6}{-10}=\frac{6}{10}\) = 0.6
Position : 6 cm behind the mirror.
Nature : Virtual and erect image.
So the image is erect and diminished.

Question 8.
Write answers to the following questions based on the data given in the table – 3.
1) What changes will come gradually in the size of an image, when we move an object away from the concave mirror?
2) In which situation inverted images formed by a concave mirror?
3) If the centre of curvature of a concave mirror is 10 cm, where the object should be placed to get an image at centere of curvature?
Answer:
1) a) If we move an object from a concave mirror to its focus (F), we will get a virtual image.
b) If we place the object at ‘F, the size of the image is infinity.
c) If we move, the object from ‘F to centre of curvature the size of the image is decreases gradually but the size of the image is bigger than that of the size of the object.
d) At ‘C the size of the image is same as the size of the object.
e) From ‘C’ to infinity distance the size of the image is smaller than the siz4 of$he object and decreases gradually.
f) Hence, the size of the image decreases if we move an object away from the focus fo the concave mirror.

2) If we place an object beyond focus (F) inverted image will be formed.

3) At 10 cm distance (or) at u = 10 cm.

9th Class Physical Science 7th Lesson Reflection of Light at Curved Surfaces InText Questions and Answers

9th Class Physical Science Textbook Page No. 111

Question 1.
Did you burn a paper by using a magnifier?
Answer:
Yes.

Question 2.
What causes burning of the paper, while doing it?
Answer:
Converging light rays through magnifier at one point on the paper.

Question 3.
Can you use a plane mirror to burn a paper instead of a magnifier lens?
Answer:
Cannot.

Question 4.
Can’t? Why?
Answer:
Plane mirror cannot converge light rays.

Question 5.
Which type of mirrors may be used to converge light rays?
Answer:
Concave mirrors.

Question 6.
Which type of reflected surface used by Archimedes?
Answer:
Curved reflected surfaces.

9th Class Physical Science Textbook Page No. 112

Question 7.
Can we burn a paper by using light rays of the torch light?
Answer:
Cannot.

Question 8.
Can’t? Why?
Answer:
The light rays coming from the torch light are not parallel rays. Hence, they cannot converge at one point on the paper with high intensity.

Question 9.
Which type of incident rays are required to get high intensity and point sized converging point?
Answer:
Parallel light rays.

Question 10.
Which line is taken as a base to draw a reflected ray to the given incident ray?
Answer:
Normal taken as base.

9th Class Physical Science Textbook Page No. 114

Question 11.
Does a concave mirror from image at focus in all situations?
Answer:
No

9th Class Physical Science Textbook Page No. 114

Question 12.
See the given figure, a set of parallel rays are falling on a convex mirror. What conclusions can you draw from this?

Answer:
The parallel rays are diverging after reflection. If we extend the reflected rays backwards, they meet at F which is focal point of convex mirror. The image formed is virtual, straight and point sized.

Question 13.
Will you get a point image if you place a paper at the focal point?
Answer:
We can get highly enlarged image at infinity when we place paper at focal point.

9th Class Physical Science Textbook Page No. 118

Question 14.
How can you find the focal length of a convex mirror?
Answer:

• The focal length of a convex mirror can be determined by introducing a convex lens between the object and the convex mirror.
• An image can be obtained with the help of a convex lens side by side with object when the convex mirror reflects the rays along the same path.
• Then, the radius of curvature (R) of the mirror is the distance between the screen and the mirror.

• The focal length ‘f of the convex mirror is calculated using the formula R (Radius of curvature)
  

Question 15.
Can we get a magnified image by a convex mirror?
Answer:
No, convex mirror cannot form magnified image.

9th Class Physical Science Textbook Page No. 119

Question 16.
How can one see an image formed on the object itself?
Answer:
When an object placed at centre of curvature the image should form at C in inverted position. So the image formed on the object itself.

Question 17.
Do you get an image when object is placed at F? Draw a ray diagram. Do the experiment.
Answer:

When an object placed at F, we can get the image at an infinite distance.

9th Class Physical Science 7th Lesson Reflection of Light at Curved Surfaces Activities

Activity – 1

1. Observation the light rays on concave and convex surfaces.
Answer:
Procedure :

1. Take a rectangular shaped (3″ x 6″) Acrylic sheet.
2. Hold the Acrylic sheet with your palm without bending it.
3. Ask your friend to focus light with a torch light on the sheet.
4. Now adjust the sheet as reflected rays are caught on a wall.
5. Now bend slowly your palm as the sheet bends inwards in the shape of concave.
6. Again ask your friend to focus the light.
7. Now bend slowly your palm as the sheet bends outwards in the shape of convex.
8. Again ask your friend to focus the light.

Observation :

1. In the first case, when without bending the sheet, reflected light is not converged at one place. Because the sheet was acted as a plane mirror.
2. In the second case, reflected light converged at one place. Because the acrylic sheet is bent inwards and it is acted as a concave mirror.
3. In the third case, reflected light rays are not converged, of course they diverged with low intensity. Because the sheet was acted as a convex mirror.

Conclusion :
Concave surfaces converge light rays and convex surfaces diverge.

Activity – 2

Question 2.
Show that a powerful source far away is needed to get parallel rays of light.
Answer:

1. Stick two pins on a thermocole block.
2. The pins are exactly parallel to each other.
3. When a source of light is kept very near, we see the shadows diverging (from the base of the pins).
4. As we move the source away from the pins, the angle of divergence gets reduced.
5. If we move the source far away we will get parallel shadows. But the light intensity reduces.
6. That means to get a beam of parallel rays all that we need is a powerful source far away.

Activity – 3

Question 3.
Identify the focus or focal point of concave mirror.
(OR)
How do you able to find the focal point of a given concave mirror? Explain it with an activity.
Answer:

1. Hold a concave mirror perpendicular to the direction of sunlight.
2. Take a small paper and slowly move it in front of the mirror and find out the point where we get smallest and brightest spot image of the sun.
3. The rays coming from the sun parallel to the concave mirror are converging at a point.
4. This point is called Focus or focal point (F) of the concave mirror.

Activity – 4

Question 4.
Find the normal to a curved surface.
(OR)
How do you find normal to a curved surface ? What is the name given to wavering point of normals, explain.
Answer:

• Take a small piece of thin foam or rubber (like the sole of a slipper).
• Put some pins in a straight line on the foam.
• All these pins are perpendicular to the plane of foam.
• If the foam is considered as a mirror, each pin would represent the normal at that point.
• Any ray incident at the point where the pin makes contact with the surface will reflect at the same angle as the incident ray made with the pin-normal.
• If we bend the foam piece inwards, we will notice that all the pins tend to converge at a point.
• If we bend the foam piece outwards, the pins seem to move away from each other or they diverge.
• This gives us an idea about spherical mirror.
• A concave mirror will be like the rubber sole bent inwards (fig. b) and the convex mirror will be like the rubber sole bent outwards (fig. c).

• For a concave mirror, like these pins all normals will converge towards a point. This point is called centre of curvature (C) of the mirror.
• For the ray R, the incident angle is the angle it makes with the radius (normal) shown as Zi and the reflected angle is shown as Zr. We know by first law of reflection Zi = Zr.

Lab Activity

Question 5.
Write the experimented method in measure the distances of object and image using concave mirror. And write the table for observations.
(OR)
Write an experimental activity which gives the information about types of images and measuring the object distance and image distance.
Answer:
Aim :
Observing the types of images formed by a concave mirror and measuring the object distance and image distance.

Material required :
A candle, paper, concave mirror, V-stand, measuring tape or meter scale.

Procedure:

1) Place the concave mirror on V-stand, a candle and meter scale as shown in figure.
2) Keep the candle at different distances from the mirror (10 cm to 80 cm) along the axis and by moving the paper find the position where we get sharp image on paper.

3) Note down the observations in table -1

4) Since we know the focal point and centre of curvature, we can re-classify the above observations as shown in the table – 2.

5) Then note down the observations in table – 2

AP State Syllabus AP Board 9th Class Physical Science Important Questions Chapter 4 Atoms and Molecules

AP State Syllabus 9th Class Physical Science Important Questions 4th Lesson Atoms and Molecules

9th Class Physical Science 4th Lesson Atoms and Molecules 1 Mark Important Questions and Answers

Question 1.
What is the difference between 2N and N₂?
Answer:
2N means two nitrogen atoms.
N₂ means one nitrogen molecule.

Question 2.
Mohan said, “O₂ differs from O,”. Do you agree? Justify.
Answer:
1) Yes, I agree with Mohan’s statement.
2) ‘O’ means single oxygen atom.
‘O₂‘ means single oxygen molecule.

Question 3.
The atomic number (Z) of an element is 6. Name the element.
Answer:
Carbon.

Question 4.
Write any one precaution in doing the experiment chromotography.
Answer:
Make sure that the ink line or mark does not touch the water.

Question 5.
In a class, a teacher asked students to write the molecular formula of Oxygen, Namitha wrote the formula as “O₂“, Raju as “O”. Which one is correct?
Answer:
Namitha is correct.
Molecular formula of oxygen is O₂.

9th Class Physical Science 4th Lesson Atoms and Molecules 2 Marks Important Questions and Answers

Question 1.
Fill the following table.

Name	Molecular Mass	No. of Particles present in molar mass
1. Atomic Oxygen	16 gr
2. Sodium	23 gr
3. Sodium chloride		6.02 × 1023 of Sodium chloride
4. Water	18 gr

Answer:

Name	Molecular Mass	No. of Particles present in molar mass
1. Atomic Oxygen	16 gr	6.02 × 1023 of oxygen atoms
2. Sodium	23 gr	6.02 × 1023 of sodium atoms
3. Sodium chloride	58.5 gr	6.02 × 1023 of Sodium chloride
4. Water	18 gr	6.02 × 1023 of water molecules

Question 2.
Compare the subatomic particles electron, proton and neutron.
Answer:

Question 3.
What are the materials used in “Conservation of mass” experiment?
Answer:
Material required for Conservation of mass:
Sodium sulphate, Barium chloride, distilled water, conical flask, spring balance, small test tube, rubber cork, thread, retort stand.

9th Class Physical Science 4th Lesson Atoms and Molecules 4 Marks Important Questions and Answers

Question 1.
Fill in the blanks in the table using the given information.

Answer:

Question 2.
Read the following information and answer.
Molecular mass of a molecule is the sum of the atomic masses of individual atoms in it.

Element	Atomic number	Atomic mass
Sodium	11	23
Oxygen	8	16
Hydrogen	1	1
Carbon	6	12

i) Find the molecular mass of Na₂CO₃.
Answer:
Molecular mass of Na₂CO₃ = (23 × 2) + 12 + (16 × 3) = 46 + 12 + 48 = 106

ii) If the molecular weight of a compound is 44. Which is made with carbon and oxygen. What its molecular formula?
Answer:
Molecular weight of a compound = 44
At. mass of Carbon = 12 Remaining at. mass = 44-12 = 32 = 16 × 2
Hence, 16 × 2 ⇒ (Oxygen atomic mass × 2) ⇒ O₂
Molecular formula = CO₂

iii) What is the unit of atomic mass?
Answer:
Unit of atomic mass = amu
atomic mass unit (amu) is defined as precisely \(\frac{1}{12}\) the mass of an atom of carbon -12.

iv) On the basis of molecular weights of NaOH and H₂O, which is heavier?
Answer:
Molecular weight of NaOH = 23+16 + 1= 40
Molecular weight of H₂O = (1 × 2)+ 16 = 2 + 16=18
Hence, NaOH is heavier than H₂O.

Question 3.
Complete the table.

Answer:

9th Class Physical Science 4th Lesson Atoms and Molecules Important Questions and Answers

9th Class Physical Science 4th Lesson Atoms and Molecules 1 Mark Important Questions and Answers

Question 1.
How did the element Helium get its name?
Answer:
Place of discovery of element can also play a role in its naming. The gas which was first discovered in the sun was named Helium. Because, Greek name for sun is helios’.

Question 2.
What is an atom?
Answer:
An atom is the smallest particle of an element that can participate in chemical reaction and retain all its properties.

Question 3.
Is ‘Na’ an element or compound? Why?
Answer:
‘Na’ is an element, because it was formed by the same atoms of ‘Na’.

Question 4.
Is O₂ an element or compound? Why?
Answer:
O₂ is a compound, because O₂ is formed by combining two oxygen atoms.

Question 5.
What is an Avogadro number? What is its value?
Answer:
The number of particles present in one mole of any substance is the Avogadro number (N_A).
This is equal to 6.022 × 10²³.

Question 6.
Which instrument is used to calculate the atomic mass exactly?
Answer:
Mass spectrometer.

Question 7.
What is atomic mass?
Answer:
The number of times one atom of given element is heavier than 1/12th part of atomic mass of carbon -12 is called its atomic mass.

Question 8.
How molecules are formed?
Answer:
A molecule is formed by the combination of different kinds of atoms that are chemically bonded together by attractive forces.

Question 9.
Why is it not possible to see an atom with naked eye?
Answer:
The size of an atom is so small i.e., less than 1 nm (1 nano metre). So we are unable to see an atom.

Question 10.
What is a chemical formula?
Answer:
The chemical formula of a compound is a symbolic representation of its composition.

Question 11.
How many atoms are present in.
i) H₂S molecule and
ii) PO₄^3- ion?
Answer:
i) The number of atoms in H₂S molecule = 2 + 1=3
ii) The number of atoms in PO₄^3- ion =1 + 4 = 5

9th Class Physical Science 4th Lesson Atoms and Molecules 2 Marks Important Questions and Answers

Question 1.
Who is called as the father of modern chemistry? What are his main contributions?
Answer:

1. Antoine Lavoisier a French scientist is called as “Father of modern chemistry”.
2. He made many important contributions to chemistry.
3. One of his contributions is law of conservation of mass.

Question 2.
State the following.
a) Law of conservation of mass
b) Law of constant proportions
Answer:
a) Law of conservation of mass :
Matter is neither created nor destroyed during a chemical reaction.
(or)
The mass of the reactants is equal to the mass of the products of chemical reaction.

b) Law of constant proportions :
A given chemical substance always contains the same elements combined in a fixed proportions by weight.

Question 3.
What are the Dalton’s proposals about the nature of matter?
Answer:
John Dalton proposed the basic theory about the nature of matter. His proposals are :

1. If mass was to be conserved, then all elements must be made up of extremely small particles called atoms.
2. If law of constant proportions is to be followed, the particles of same substance couldn’t be dissimilar.

Question 4.
What is the proposal of Indian sage Kanada, about atom?
Answer:

1. About 2600 years ago, an Indian sage called Kanada, postulated atoms in his Vaishesika sutra”.
2. He proposed that all forms of matter are composed of very small particles known as “Anu”.
3. Each “Anu” may be made up of still smaller particles called “Paramanu”.

Question 5.
What is the use of symbols for elements?
Answer:

1. We know that chemistry involves a lot of reactions.
2. It will be a waste of time to write the full name of the elements and compounds every time to describe a reaction.
3. To avoid this we use symbols for naming the elements and formulae to represent compounds.

Question 6.
What are the characteristics of a symbol?
Answer:
1) A symbol can have either one or two letters of English.
Ex : H, He, N, Ne, etc.

2) The first letter of the symbol is always upper case and the second letter is always lower case.
Ex :
1) Al, Cr, Cl, etc. is the right method to represent elements.
2) CL, bE, he, etc. is the wrong method to represent elements.

Question 7.
In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g of water, and 8.2 g of sodium ethanoate. Show that these observations are in agreement with law of conservation of mass.
Answer:
Sodium carbonate + Ethanoic acid → Sodium ethanoate + Carbon dioxide + Water
The total mass of reactants = 5.3 + 6 = 11.3 g
The total mass of products = 2.2 + 0.9 + 8.2 = 11.3 g
∴ Total mass of reactants = Total mass of products
So these observations are in agreement with law of conservation of mass.

Question 8.
Hydrogen and oxygen combine in the ratio of 1 : 8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Answer:
According to data 1 g of hydrogen is reacting with 8 g of oxygen.
So amount of oxygen would be required to react completely with 3 g of hydrogen
= 3 x 8 = 24 g

Question 9.
Calculate formula unit weight of ZnO, Na₂O, K₂CO₃ (Given atomic weight of Zn = 654)
Answer:
Formula unit weight of ZnO = 65 + 16 = 81 u
Formula unit weight of Na₂O = 2 × 23 +16 = 62u
Formula unit weight of K₂CO₃ = 2 × 39 + 12 + 3 × 16 = 138 u

Question 10.
Calculate the number of moles for the following.
i) 52 g of He (finding mole from mass).
ii) 12.044 × 10₂₃ number of He atoms (finding mole from number of particles).
Answer:

Question 11.
If one mole of carbon atom weighs 12 g. What is the mass of 1 atom of carbon?
Answer:

Question 12.
When 3 g of carbon is burnt in 8 g of oxygen 11 g of carbon dioxide is produced. What mass of carbon dioxide is formed when 3 g of carbon is burnt in 50 g of oxygen.
Answer:
3 g of carbon react with 8 g of oxygen to form 11 g of carbon dioxide.
Ratio of carbon and oxygen = 3 : 8
The amount oxygen react with 3g of carbon = 3 × 8 = 24.
So the amount of carbon dioxide formed = 3 + 24 = 27 g.

Question 13.
Given the names of the elements present in the following compounds.
a) Quick lime
b) Hydrogen bromide
c) Baking soda
d) Potassium sulphate
Answer:

Compound	Formula	Elements
a) Quick lime	CaO	Calcium, oxygen
b) Hydrogen bromide	HB2	Hydrogen, bromine
c) Baking soda	NaHCO3	Sodium, hydrogen, carbon, oxygen
d) Potassium sulphate	K2SO4	Potassium, sulphur, oxygen

Question 14.
Calculate number of sulphur (Sg) present in 16 g of solid sulphur.
Answer:
Molecular weight of sulphur = 8 × 32 = 256 g.
256 g of sulphur contains 6.022 × 10₂₃ molecules.
Number of molecules present in 16 g of sulphur = \(\frac{16}{256}\) × 6.022 × 10²³
= 3.77 × 10²² molecules

Question 15.
Anitha wrote the formula for oxygen molecule as 20. Is it correct or not? Why?
Answer:

1. It is not correct.
2. The formula of oxygen molecule is O₂.
3. 2O shows two separate atoms of oxygen.
4. O₂ shows molecule of oxygen.

9th Class Physical Science 4th Lesson Atoms and Molecules 4 Marks Important Questions and Answers

Question 1.
How elements got their names? Explain with examples.
Answer:
I: Sometimes elements are named based on their property.
Ex :
1) The Latin name for water is “hydro”.
So the element that combined with oxygen to give water was named as ‘hydrogen’.

2) The Latin word for acid is ‘oxy’.
Hence the gas that forms acid is ‘oxygen’.

II. Place of discovery of element can also play a role in its naming.
Ex : The gas that was first discovered in the sun (Greek name for the sun is “helios”) was named as ‘helium’.

III. Sometimes the elements were named to honour the scientists.
Ex : Einsteinium, Fermium, Rutherfordium and Mendelevium, etc.

Question 2.
Define the following terms.
a) Atomicity
b) Valency
c) Ions
Answer:
a) Atomicity :
The number of atoms constituting a molecule is known as its atomicity.

Ex :
1) Na is monoatomic
2) O₂ is diatomic
3) O₃ is triatomic

b) Valency :
Atoms of the elements have power to combine with atoms of other elements. This is known as valency.
Ex :
1) Valency of carbon is 4.
2) Valency of oxygen is 2.
3) Valency of hydrogen is 1.

c) Ions:
1) Ions may be a single charged atoms or a group of atoms that have a net charge on them.
2) A negatively charged ion is called anion and the positive charge ion is cation.
Ex : Na⁺, Cu⁺², S^2-, N^3-, etc.

Question 3.
Explain the method of writing a formula to a compound using criss – cross method, with the help of an example.
Answer:
The following steps should be taken while attempting to write a chemical formula using criss – cross method.
Ex : Take sodium carbonate as an example.
1) Write the symbols of atoms or group of atoms side by side, usually the cation first.
NaCO₃

2) Write the valency of each atom or group of atoms on the top of its symbol.
Na¹ (CO₃)²

3) Divide the valency number by their highest common factor if any to get the simple ratio.
Na¹ (CO₃)²

4) Interchange the valency and write the numbers to the lower right of the constituents as subscript.
Na₂(CO₃)₁

5) If any constituent receives the number 1, ignore it while writing the formula.
Na₂CO₃

6) If group of atoms received the number more than 1, enclose it within brackets. Hence the formula for the sodium carbonate is Na₂CO₃.

Question 4.
Define the terms :
a) molecular mass,
b) formula unit mass,
c) mole and
d) molar mass.
Answer:
a) Molecular mass :
The molecular mass of a substance is the sum of the atomic masses of all the atoms in a molecule of a substance.

b) Formula unit mass :
The formula unit mass of a substance is a sum of the atomic masses of all atoms in a formula unit of a compound.

c) Mole :
1) One mole of a substance is the amount of the substance which contains as many particles or entities that are equal to the atoms present in exactly 12 grams of C¹² isotope.
2) The number of particles present in one mole of any substance has a fixed value of 6.022 × 10²³. This number is called Avogadro’s constant (N_A).

d) Molar mass :
The mass of 1 mole of a substance which is expressed in grams is called its molar mass.

Question 5.
What are the main postulates of Dalton’s atomic theory?
Answer:
The main postulates of Dalton’s atomic theory are :

1. Matter consists of indivisible particles called atoms.
2. Atoms are neither created nor destroyed in a chemical reaction, but atoms will reorganize.
3. All the atoms of a given element have identical mass and chemical properties.
4. Atoms of different elements have different masses and chemical properties.
5. Compounds are formed when atoms of different elements combine in simple whole number ratios i.e., chemical change is the union or separation of atoms as a whole number.

Question 6.
Draw the pie diagram to understand the atomic mass and explain it.
Answer:

Explanation :

1. Let us assume the circle in the diagram represents mass of one carbon – 12.
2. It is divided into 12 equal parts as shown in the figure.
3. Each part represents 1/12th of atomic mass of one carbon -12.

Atomic mass unit :
One atomic mass unit is defined as the mass exactly one-twelfth the atomic mass of carbon – 12 isotope.

Question 7.
Illustrate the concept of mole through a diagram.
Answer:
Mole :

1. One mole of a substance is the amount of the substance which contains as many particles (atoms, molecules etc.) or entities that are equal to the atoms present in exactly 12 grams of ¹²C isotope.
2. The number of particles present in one mole of any substance has a fixed value of 6.022 × 10²³. This number is called Avogadro’s constant (N_A).

Question 8.
How can you appreciate John Dalton for proposing his atomic theory?
Answer:

• We know, development of science and technology is a combined effort of Roman scientists.
• The zeal to know or discover something new, leads the scientists for their discoveries.
• One of such is the atomic theory proposed by Dalton, based on Lavoisier’s law of conservation of mass and Proust’s law of constant proportions.
• Dalton said atom is indivisible.
• This proposal lead to discover many new things by various scientists and to unveil the complete structure of atom.
• Hence Dalton’s contribution is highly appreciable.

Question 9.
How do you feel after studying the symbols and formulae of different elements and compounds?
Answer:

• In my earlier class I came to know that chemistry is nowhere but in our kitchen.
• I used to call so many chemicals with their names.
• Now I am able to call them with their symbols and formulae.
• For example 1 can call the common salt as NaCl.
• This thrills me alot, and I am curious to know the formulae of so many common household substances.
• This is very helpful for my higher studies.

Question 10.
Describe the experiment conducted by Joseph L. Proust, which lead him to propose law of constant proportions.
Answer:

• Proust took two samples of copper carbonate, one from nature and another prepared in the lab.
• These two samples are chemically decomposed to find percentage of copper, carbon and oxygen.
• The results obtained are given in the table.

Weight percentage of	Natural sample	Synthetic sample
Copper	51.35	51.35
Carbon	38.91	38.91
Oxygen	9.74	9.74

• From the above table we observe that the percentage of copper, carbon and oxygen atoms in two samples are same.
• Based on this observation Proust proposed the law of constant proportions as “A given chemical substance always contains the same elements combined in a fixed proportions by weight”.

Question 11.
Write down the formulae of these compounds, using criss – cross method?
i) Sodium oxide
ii) Aluminium chloride
iii) Sodium sulphate
iv) Magnesium hydroxide
Answer:

Question 12.
Write down the names of compounds represented by the following formulae and also write the anion, cation.
i) Al₂(SO₄)₃
ii) CaCl₂
iii) K₂SO₄
iv) KNO₃
v) CaCO₃
Answer:

Question 13.
What are the rules you have to follow while writing a chemical formula?
Answer:

1. The valencies or charges on the ion must balance.
2. When a compound consists of metal and non-metal, the name of the symbol of metal is written first, eg : Calcium oxide (CaO)
3. In compounds formed with poly atomic ions, the ion is enclosed in a bracket before writing the number to indicate the ratio.

Question 14.
Calculate the molecular weight H₂, O₂, Cl₂, CO₂, CH₄, C₂H₆, C₂H₄, NH₃, CH₃OH.
Answer:
Molecular weight of H₂ = 2 × 1 = 2 u
Molecular weight of O₂ = 2 × 16 = 32 u
Molecular weight of Cl₂ = 2 × 35.5 = 71 U
Molecular weight of CO₂ = 12 + 2 × 16 = 44 u
Molecular weight of CH₄ = 12 + 4 × 1 = 16 u
Molecular weight of C₂H₆ = 2 × 12 + 6 × 1= 30 u
Molecular weight of C₂H₄ = 2 × 12 + 4 × 1= 28 u
Molecular weight of NH₃ = 14 + 3 × 1 = 17 u
Molecular weight of CH₃OH = 12 + 4 × 1 + 16 = 32 u

Question 15.
a) What is atomicity?
b) Give examples.
c) Why do elements have different atomicities?
Answer:
a) Atomicity:
The number of atoms constituting a molecule is known as its ‘atomicity’.

b) Examples :
A molecule of hydrogen consists of two atoms of hydrogen. Here the atomocity is two. Hence it is known as a diatomic molecule. Helium (He), Argon (Ar) exist as single atom. Hence they are known as monoatomic.
Ozone (O₃) has tetratomic
Sulphur (S₈) has octatomic

c) Every element has a definite combining capacity, that determines the atomicity of its molecules. Every element reacts with other element according to its combining capacity, which we call as its valency.

SCERT AP Board 9th Class Social Solutions 23rd Lesson Disaster Management Textbook Questions and Answers.

AP State Syllabus 9th Class Social Studies Solutions 23rd Disaster Management

9th Class Social Studies 23rd Lesson Disaster Management Textbook Questions and Answers

Improve Your Learning

Question 1.
Explain how a natural hazard becomes a disaster.
Answer:

• A natural hazard is a natural event of unusual magnitude that people don’t expect and cannot control.
• Natural hazards threaten people’s lives and their activities and can forever change their ways of living.
• A natural hazard event can become a natural disaster when causes the destruction of people’s property or their injury and/or death.

Question 2.
What is Terrorism? What are the motives of terrorists?
Answer:
A common definition of terrorism is the systematic use or threatened use of violence to intimidate a population or government and thereby effect political, religious or ideological change.
Motives of terrorism :

• Terrorism is a type of violence used tactically in peace, conflict and war.
• The motivation of terrorists are quiet various depending on what they hope to accomplish.
• The majority of the motives can be broken down into three broad areas: rational, psychological and cultural.
• Although some motives are difficult for the majority of the world to comprehend given a motive, a terrorist group has a purpose for violence.

Question 3.
What safety measures should be followed to avoid fire accidents?
Answer:
Safety measures to be followed to avoid fire accidents:

• Prevention of fire is necessary for avoiding accidents.
• Never leave the kitchen during cooking, no matter what the circumstance.
• All the inflammable things or liquids should not be kept near the fire.
• Electrical appliances should have incorporated in an automatic cut off feature for some time. Timers can be used for these.
• Wear suitable dresses while cooking.
• Installation of fire detectors in the house will alert automatically the fire department.
• One should not smoke in bed/throw burning buds here and there.
• One should not play crackers etc., near the house.
• One should not keep match boxes, lighter etc., at the reach of the children.
• One should not keep agarbattis carelessly.
• One should not make fire when wind is blowing.
• One should close the regulator of the gas cylinder properly etc.

Question 4.
What are the main causes of road accidents? How can we reduce the road accidents?
Answer:
The main causes of road accidents:

1. Alcohol & drunk – driving.
2. Speeding
3. Weather related
4. Hydroplanning
5. Animals in road.
6. Street racing.
7. Cell phones.
8. Music, CD players, Radio distractions
9. Driver fatigue
10. Suicide car accidents.

Steps to reduce road accidents :

1. Strict enforcement of speed limits.
2. Heavy penalty should be imposed on all those who cross speed limits.
3. Lower age limit for 2 wheeler and heavy vehicle licence should be raised to 21.
4. Driving tests for issue of driving license is to be made more stringent and fool proof.
5. Helmet should be made compulsory by law.
6. Existing traffic rules should be strictly enforced, etc.

Question 5.
Terrorist attacks cause loss of life and wealth. What are the precautions to be taken to prevent these activities?
Answer:

• Devastating acts have left many concerned about the possibility of future incidents.
• Taking preparatory action can reassure us that we can exert a measure of control even in the face of such events.
• Finding out what can happen is the first step. Then develop a disaster plan.
• Create an emergency communications plan.
• Establish a meeting place.
• Assemble a disaster supplies kit.
• If disaster strikes :
  a) Remain calm and be patient.
  b) Follow the instructions of local emergency officials.
  c) If the disaster occurs near you, check for injuries. Give first aid and get help for seriously injured people.

Thus we can protect from terrorist attacks.

Question 6.
Identify the causes of rail accidents.
Answer:
Causes of rail accidents :

1. Lack of proper maintenance.
2. Human error or sabotage.

Question 7.
List out the reasons and risk inducing factors in your home, school or village.
Answer:
Three risk inducing factors :

1. In my home: Nothing.
2. In my school:
   a. There is a big pit in our school. I think it is dangerous.
   b. We have 3 storeyed building as our school. The little children are in the third stair. I think it is also a risk factor.
3. In my village : My village is in earthquake zone.

Question 8.
Locate the following places attacked by terrorists in the India map.
a) Mumbai
b) Hyderabad
c) Bhagalpur
d) Kumbakonam
e) Bengaluru
Answer:

Question 9.
Write about an incident related disaster you know.
Answer:
Some years ago we went to Marina beach in Chennai. We enjoyed a lot by playing there. We built some structures in the sand. We ate peanuts, groundnuts, mango pieces, etc. on our return we walked far away from the sea. Suddenly we heard the noises of the people in the beach. Then we saw a big wave. Many were drowned and lost their lives. We ran very fast from the place. By god’s grace we are still alive.

Question 10.
Read the para under the title ‘Fire Accidents’ on page 281 and comment on it.
Fire Accidents :
The 2004 fire in a school in Kumbakonam, Tamilnadu sparked ofT debates and arguments on the safety of schools in the*ountry. 93 innocent people were charred to death. The main causes of this fire were lack of awareness amongst children and teachers as to what to do in case of a fire, lack of preparedness, kitchen close to the classroom etc. However, incidents like these are not new.
Answer:
Fire accidents can be due to various reasons. They include open flames such as a candle being accidentally being knocked over or through electrical faults. It is important to know the fire safety rules because fire accidents can result in disastrous personal injury and distressing damage. Fire safety plans are to be planned.

Question 11.
Collect information from newspapers and magazines about the human induced disaster that have taken place in the past few years in your state. Find out, what measures are being taken in your area to reduce such risks in the future.
Answer:
Nowadays road accidents became a common scenario in India. The main reasons behind the road accidents are not obeying speed limits, poor roads, drinking and driving, rash driving, aggressive driving etc.

Information about road accidents in Telangana and Andhra Pradesh :

Year	No. of accidents	No. of deaths
2004	39,390	10,621
2005	38,913	11,098
2006	42,867	12,606
2007	45,163	13,791
2008	46,389	14,529
2009	45,977	15,203
2010	44,570	15,696
2011	42,869	15,100
2012	41,712	14,975

On an average of last 6 years the number of accidents are 44,446 and the number of deaths are 14,882 in Telangana and Andhra Pradesh.
The following measures are taken to control the road accidents in Andhra Pradesh :

1. Increased traffic fines in India.
2. Suspending licence for drunken drivers.
3. Established traffic courts.
4. Started traffic awareness programmes for drivers.

Question 12.
List the various losses incurred due to terrorism.
Answer:

1. Fear in people
2. Psychological problems in people
3. Negative effect on tourism
4. Financial or economic losses
5. Unstable governments and
6. Loss of human lives, etc.

9th Class Social Studies 23rd Lesson Disaster Management Activities

Question 1.
From the nearest fire station, find out what are the other simple Do’s and Don’ts that you can follow and awareness to reduce fire accidents.
Answer:
I live in Vijayawada. We have fire station in Krishnalanka. I visited that and learnt the following. Do’s :

• Do have an adult always present when cooking is going on the kitchen. Children should not be allowed alone.
  Do keep hair tied back and do not wear synthetic clothes when you are cooking.
  Do make sure that the curtains on the window near the stove are tied back and will not blow on the flame or burner.
  Do check to make sure that the gas burner is turned off immediately if the fire is not ignited and also switched off immediately after cooking.
  Do keep matches out of the reach of children, etc.

Don’ts :

• Don’t put any clothes near the stove.
• Don’t wear loose fitting clothes or chunnies, etc.
• Don’t store spray cans or cans carrying inflammable items near the stove.
• Don’t let small children near an open oven door.
• Don’t lean against the stove to keep warm, etc.

Question 2.
Identify recent terrorist acts that have taken place in India, and discuss the possible effects of these acts on children.
Answer:
Terrorist attack at Amarnath on July 11, 2017 is recent attack that have taken place in India.

Many children are exposed to trauma and life-threatening solution, duringthe last few decades, thousands of children have been exposed to terrorism. The attacks significantly, affect the mental health of the children. Terrorist attacks and their aftermath have had a powerful impact on children and their families. Media and television exposure of terrorist events throughout the world has increased during the past few years. There is increasing concern about the effects of this exposure on children who witness these violent images. Recent studies have examined the effect of remote exposure of terrorist attacks and have shown a significant clinical impact on children and families.

AP State Syllabus AP Board 9th Class Physical Science Important Questions Chapter 5 What is inside the Atom?

AP State Syllabus 9th Class Physical Science Important Questions 5th Lesson What is inside the Atom?

9th Class Physical Science 5th Lesson What is inside the Atom? 1 Mark Important Questions and Answers

Question 1.
Write any two limitations of Rutherford’s atomic model.
Answer:

• The revolving electron would lose energy continuously and get directed towards positively charged nucleus and eventually crash into the nucleus.
• If this is true, the atoms would become highly unstable and the matter would not exist, but matter exists.

Question 2.
In Rutherford’s experiment, when the alpha particles hit the foil, Rutherford expected that all the alpha particles would be deflected by small angles. Why did Rutherford expect the above observation?
Answer:
Rutherford thought that positive charge is distributed throughout the atom.

Question 3.
Write an application of isotopes in the field of medicine.
Answer:

• The isotope of iodine is used in the treatment of goitre.
• The istope of cobalt is used in the treatment of cancer.

9th Class Physical Science 5th Lesson What is inside the Atom? 2 Marks Important Questions and Answers

Question 1.
What is valency? Write valency of hydrogen.
Answer:

• The number of electrons present in outer most orbit of an atom is called its valency.
• Valency of hydrogen is 1.

Question 2.
Observe the table given below.

Shell	Shell No	Maximum number of electrons in a shell
K	1	2(1)2 = 2
L	2	2(2)2 = 8
M	3	2 (3)2 = 18
N	4	2(4)2 = 32

Answer the following questions.
i) Which Shell has highest number of electrons?
ii) Write the general form of the formula to find maximum number of electrons in each shell?
Answer:
i) 0 Shell ‘N’.
ii) 2n² (n = 1, 2, 3, ……..)

Question 3.
Convert 36g of water into mole?
Answer:
Water molecular formula = H₂O
At.wt. of water = (2 × 1) + 16 = 18
1 mole, water = 18 gr.
36g. of water = \(\frac{36}{18}\) = 2 moles

9th Class Physical Science 5th Lesson What is inside the Atom? 4 Marks Important Questions and Answers

Question 1.
Fill the blanks in the table using the given information. (Isotopes are not included).

Answer:

Question 2.
Fill in the missing information in the table given below.

Answer:

Question 3.
Draw the figures showing arrangement of electrons for the given elements.
1. Helium, Oxygen, Argon.
Answer:
1) Helium
2) Oxygen
3) Argon

2. How many neutrons are present in the nucleus of Sodium?
Answer:
Sodium = ²³₁₁Na
Neutrons = 23-11 = 12

Question 4.
a) Draw neat diagrams indicating the nucleus and arragement of electrons in different shell for the following elements?
i) Helium
ii) Carbon
iii) Argon
Answer:

b) Which of the above element is unstable? Why?
Answer:
Carbon is unstable. The nudes of carbon-14 atoms are unstable because they have too many neutrons relative to protons, so they gradually decay.

9th Class Physical Science 5th Lesson What is inside the Atom? Important Questions and Answers

9th Class Physical Science 5th Lesson What is inside the Atom? 1 Mark Important Questions and Answers

Question 1.
Write the names of isotopes of Hydrogen.
Answer:
Hydrogen, deuterium, tritium.

Question 2.
Which element has maximum number of isotopes?
Answer:
Cesium and Helium are the elements having maximum number of isotopes.

Question 3.
What is maximum number of electrons present in M-shell?
Answer:
Maximum number of electrons present in M-shell is 2 × 32 = 2 × 9 = 18.

Question 4.
Which atom doesn’t contain neutron in its nuclear?
Answer:
Hydrogen.

Question 5.
Show the arrangement of electrons in phosphorus through a diagram.
Answer:
Atomic number of phosphorus is 15.
Distribution of electrons : 2, 8, 5.

Question 6.
Who proposed rules for electron distribution in an atom?
Answer:
Bohr and Bury.

Question 7.
What is the first rule of Bohr and Bury for electron distribution in an atom?
Answer:
The maximum number of electrons present in a shell is given by the formula 2n², where ‘n’ is the shell number, which takes values 1, 2, 3, 4,

Question 8.
Write the second principle of Bohr – Bury.
Answer:
Each energy level or electron shell is further divided into sub-shells. The maximum number of electrons that can be accommodated in each shell is 8.

Question 9.
Write the third law of Bohr – Bury.
Answer:
Electrons cannot be filled in a given shell unless the inner shells are completely filled i.e., shells are filled in step-wise manner.

Question 10.
What is an octet?
Answer:
An outermost shell which has 8 electrons is said to possess an octet.

Question 11.
Define atomic number.
Answer:
Atomic number :
Atomic number is the number of protons in the nucleus of an atom, denoted by ‘Z’.

Question 12.
Define atomic mass number.
Answer:
Atomic mass number:
Atomic mass number is the number of protons plus the number of neutrons, denoted by A.
∵ A = Z + N

Question 13.
On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.
Answer:
The negative and positive charges are equal in magnitude are present in atom. So, the atom as a whole is electrically neutral as whole according to Thomson model.

Question 14.
On the basis of Rutherford model of an atom, which sub-atomic particle is present in the nuclear of an atom?
Answer:
α – particles are repelled by the nucleus. So it contains positive charged particle that is proton.

9th Class Physical Science 5th Lesson What is inside the Atom? 2 Marks Important Questions and Answers

Question 1.
What are the postulates of Thomson’s model of the atom?
Answer:
J.J. Thomson proposed a model of atom in 1898. The main postulates are

1. An atom is considered to be a sphere of uniform positive charge and electrons are embedded into it.
2. The total mass of the atom is considered to be uniformly distributed throughout the atom.
3. The negative and the positive charges are supposed to cancel out the atom as a whole is electrically neutral.

This model is commonly known as plum pudding model or watermelon model.

Question 2.
What are the features of Rutherford’s model of atom?
Answer:
In 1909, Rutherford proposed a model of atom based on the alpha particle scattering experiment. The main features are

1. All the positively charged material in an atom formed a small dense centre, called the nucleus of the atom. The electrons were not a part of nucleus.
2. The negatively charged electrons revolve around the nucleus in well-defined orbits.
3. The size of the nucleus is very small as compared to the size of the atom.

This model is known as planetary model because the electrons revolve around the nucleus as planets revolve around the sun.

This model failed to explain the stability of atom.

Question 3.
Write the rules proposed by Bohr – Bury for electron distribution.
Answer:
Bohr-Bury proposed the following rules for electron distribution.
Rule – 1 :
The maximum number of electrons that can be accommodated in each shell is given by a formula 2n2. Where n is the shell number, which takes the values 1, 2, 3,….
Ex : For K shell, n = 1

∴ Maximum number of electrons in K shell = 2(1)2 = 2 × 1=2

Rule – 2 : Each energy level or electron shell is further divided into subshell. The maximum number of electrons that can be accommodated in each subshell is 8.

Rule – 3: Electron cannot be filled in a given shell unless the inner shells are completely filled.

Question 4.
Explain the distribution of electrons in oxygen atom using Bohr-Bury principle.
Answer:

1. Atomic number of oxygen is 8.
2. Hence it has 8 protons and 8 electrons.

Step -1 :
The K-shell can accommodate maximum 2 electrons, so the first 2 electrons fill the shell of n = 1.

Step – 2 :
The other 6 electrons will fill the higher shell n = 2 or the L-shell.
Step – 3 :
Then the electronic structure for oxygen atom is 2, 6.

Question 5.
Fluorine atom contains 7 electrons in the outermost shell. But its valency is ‘1’. Explain.
Answer:

• Valency is the number of electrons present in the outer most orbit of an atom.
• The distribution of electrons in fluorine (atomic number 9) is 2, 7.
• Hence the valency of fluorine could be 7.
• But it is easier to fluorine to gain one electron for becoming octet.
• Hence its valency is determined by subtracting seven electrons from 8 and which gives you a valency ‘1’ for fluorine.

Question 6.
What is the importance of valency?
Answer:
1) An atom with 8 electrons or an octet in their outer most shell is chemically stable or does not combine other atoms.
Ex : Ne, Ar, etc.

2) An atom with duplet or 2 electrons in its outer most shell is also more stable when there is only one shell present in it.
Ex : He

3) Atoms of an element thus react with other atoms. So as to achieve an octet in their shell.

4) When elements reacts to form compounds, their atoms must be combining in such a way that they can attain the stable electron distribution of noble gases or inert gases.

Question 7.
How can an atom achieve octet?
Answer:
An atom can achieve an octet by two ways.

1. One by transfer of electrons.
2. Other by sharing of electrons.
3. Both the processes results in the formation of bonds between atoms.

Question 8.
Explain the notation : \({ }_{9}^{19} \mathrm{F}\)
Answer:

• F is the symbol of element (Fluorine).
• 9 is the atomic number.
• 19 is the mass number.
• Hence fluorine has 9 protons and (19 – 9 = 10) 10 neutrons in its nucleus.
• 9 electrons are revolving around the nucleus.

Question 9.
Define isotope and give two examples.
Answer:
Isotope :
The atoms of the same element which have the same number of protons but have different number of neutrons are called isotopes.

Question 10.
“Sulphur shows multiple valency.” Explain this.
Answer:
a) Atomic number of sulphur is 16.
b) The distribution of electrons is 2, 8, 6.
c) Hence the valency should be ’6′.
d) But it is easier to sulphur to gain 2 electrons than loosing 6 electrons to become octet. Hence its valency would become 2.
e) So, sulphur shows multiple valency, i.e., ‘2’ or ‘6’.

Question 11.
Show the arrangement of electrons in first 18 elements schematically.
Answer:

Question 12.
What are the applications of isotopes in our daily life?
Answer:
Applications of isotopes :

1. Some isotopes are used for solving chemical and medical mysteries.
2. Isotopes are also commonly used in the laboratory to investigate the steps of a chemical reaction.
3. The isotope of uranium is used as a fuel in nuclear reactors.
4. The isotope of iodine is used in the treatment of goitre.
5. The isotope of cobalt is used in the treatment of cancer.

Question 13.
If an atom contains one electron and one proton, will it carry any charge or not?
Answer:
It will not carry any charge because proton is positively charged particle and electron is negatively charged particle. So they would neutralise each other.

Question 14.
What do you think would be the observation if the a – particle scattering experiment is carried out using a foil of metal other than gold?
Answer:
Gold has highest malleability and ductility. Extremely very thin foil can be prepared by using Gold, which is not possible with other metals. So, we will not get same type of results using other metals.

Question 15.
Helium atom has an atomic mass of 4u and two protons in its nucleus. How many neutrons does it have?
Answer:
Atomic mass due to protons = 2 × 1 = 2 u
Neutrons have almost same mass as protons.
Mass of neutrons = 4 – 2 = 2u
∴ Number of neutrons = 2

Question 16.
Write the distribution of electrons in carbon and sodium atoms.
Answer:
Distribution of electrons in carbon is 2, 4.
Distribution of electrons in sodium is 2, 8, 1.

Question 17.
If K and L shells of an atom are full, then what would be the total number of electrons in the atom?
Answer:
Number of electrons present in K shell = 2(1)² = 2 × 1=2
Number of electrons present in L shell = 2(2)² = 2 × 4 = 8
Total number of electrons in the atom = 2 + 8 = 10

Question 18.
If number of electrons in an atom is 8 and number of protons is also 8, then
i) what is the atomic number of atom?
ii) what is the charge on the atom?
Answer:
i) The atomic number of atom is 8.
ii) The electronic configuration of atom is 2, 6. By gaining two electrons it will get nearest inert gas configuration Neon. So, the charge on the atom is – 2.

Question 19.
Chlorine occurs in two isotopic forms that is \({ }_{17}^{35} \mathrm{Cl}\) and \({ }_{17}^{37} \mathrm{Cl}\). The percentage of these forms are 75% and 25% respectively. Find atomic weight of chlorine atom?
Answer:
The atomic mass of an element is taken as an average mass of all the naturally occurring atoms of the sample element.
The average atomic mass of chlorine atom on the bases of above data

Question 20.
For the symbol H, D and T tabulate three sub atomic particles found in each of them.
Answer:

Question 21.
Na⁺ has completely filled K and L shells. Explain.
Electron configuration of Na+ is 2, 8.
So, sodium has completed filled K and L shells because the maximum number of electrons filled in K and L shells are 2 and 8 electrons respectively.

Question 22.
If Bromine atom is available in the form of say, two isotopes \({ }_{35}^{79} \mathrm{Br}\)(49.7%) and \({ }_{35}^{81} \mathrm{Br}\) (50.3%), calculate the average atomic mass of Bromine atom.
Answer:

Question 23.
The average atomic mass of sample of an element X is 16.2 u. What are the percentages of isotopes \({ }_{8}^{16} \mathrm{X}\) and \({ }_{8}^{18} \mathrm{X}\)?
Answer:

∴ The percentage of first isotope is 90 and percentage of second isotope is 10.

Question 24.
If Z = 3, what would be the valency of the elements? Also, name the element?
Answer:
Electronic configuration of element is 2, 1 and the element is Lithium.
The element will get nearest inert gas Helium configuration by loosing one electron. So its valency is 1.

Question 25.
Composition of nuclei of two atomic species X and Y are given as under.

	X	Y
Protons	6	6
Neutrons	6	8

Give the mass number of X and Y. What is the relation between the two species?
Answer:
Mass number of X = 6 + 6 = 12
Mass number of Y = 6 + 8 = 14
So these two species have same atomic number (same number of protons) and different mass numbers. Therefore these two species are isotopes.

9th Class Physical Science 5th Lesson What is inside the Atom? 4 Marks Important Questions and Answers

Question 1.
How did the idea of sub-atomic particles evolve?
Answer:

• According to Dalton, atom is indivisible.
• But Michael Faraday’s experiments on electrolysis proved that atoms were acquiring negative charge during electrolysis.
• This is contradiction to Dalton’s theory.
• This lead to an idea that there must exist some tiny particles in atom which are responsible for atom to behave sometimes as charged particles.
• As atom is considered as electrically neutral, it probably had equal number of positive and negative constituents to maintain electrical neutrality.
• This gave scope to think about sub-atomic particles.

Question 2.
How do we determine the atomic mass of an element with its isotopes?
Answer:

• In nature, most elements occur as a mixture of two or more isotopes, each isotope has a certain percentage of natural occurrence.
• The atomic mass of an element is taken as an average mass of all the naturally occuring atoms of the sample element.
  Ex : Let us calculate the atomic mass of chlorine.
• Isotope of Cl occurs in nature, in two isotopic forms, with masses 35 units and 37 units.
• The isotope with mass 35 is present in 75% in nature.
• The isotope with mass 37 is present in 25% in nature.
• The average mass of chlorine is
  

Question 3.
Describe the Rutherford’s alpha particle scattering experiment. What are the conclu¬sions of this experiment.
Answer:

Rutherford conducted alpha particle scattering experiment in 1909 to study the atom.

1. The stream of alpha particles from a source having considerable energy is directed towards a very thin gold foil.
2. The gold foil was placed inside a detector in such a way that the detector would show a flash of light when an alpha particle struck it.
3. The entire arrangement was kept in a vacuum chamber.
4. Rutherford did not expect to see large deflections of alpha particles based on Thomson’s model.
5. But Rutherford observed the deflection of alpha particles through very large angles and a few alpha particles were reflected right back.
6. From this observation, Rutherford concluded as follows.

Conclusions :

1. Most of the space inside the atom is empty.
2. All the positive charge must be concentrated in a very small space within the atom and he named it as ‘nucleus’.

Question 4.
What information do you know from \({ }_{17}^{35} \mathrm{X}\)?
Answer:
Given that \({ }_{17}^{35} \mathrm{X}\)
a) The atomic number of element is 17.
b) Hence the element is chlorine, symbol is ‘Cl’.
c) Number of protons = 17.
d) Number of electrons = 17.
e) Mass number = 35.
f) Number of neutrons = 35-17 = 18
g) Distribution of electrons in shells

h) Valency is ‘l’.
i) It gains one electron to become octet.