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SCERT AP Board 8th Class Social Solutions 3rd Lesson Earth Movements and Seasons Textbook Questions and Answers.

AP State Syllabus 8th Class Social Studies Solutions 3rd Lesson Earth Movements and Seasons

8th Class Social Studies 3rd Lesson Earth Movements and Seasons Textbook Questions and Answers

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Question 1.
Do you think there is any correlation between the crops grown in your region and the seasons? Find out by discussing with your eiders and friends and write a short essay on it.
Answer:
Ours is a small village Anther vedipalem in East Godavari district. In our area, we have 3 crop seasons – Kharif, Rabi and Zaid. The farmers cultivate paddy and maize in Kharif season. This season is upto October and November. Rabi is cultivated as winter crop. In Rabi also some cultivate paddy and some cereals. Duration of this season is upto March and April. After that some fruits and vegetables are grown in the Zaid season. In addition to these we have coconut plantations which give fruits throughout the year. Due to these reasons there is correlation between crops and seasons.

Question 2.
Why do you think Andhra Pradesh does not receive any snowfall during winter months?
Answer:
Snow forms in the clouds that are below freezing. Andhra Pradesh is in tropical belt. To get snow the temperatures in Andhra Pradesh are not enough cold. So Andhra Pradesh does not receive any snowfall during winter season.

Question 3.
We have a rainy season. How do you think it is related to the movement of the Earth and the pattern of Sun’s rays? Does it occur in the summer or winter or in the season in between?
Answer:
The seasons occur due to the revolution and the pattern of Sun’s rays. During summer the Sun’s rays fall straightly on our area. Then the air in the atmosphere gets heated and moves up by forming low pressure belt. The winds from high pressure belt from the Indian ocean blow to this area and give rains. We receive rains after summer and in the beginning of winter due to these seasonal winds-monsoons.

Question 4.
Collect information about time of Sunrise and Sunset for different months of the year in your place (you can look up the local newspaper for this). Calculate the duration of day and night- how many hours every day – for every month. Do you see any pattern in this?
Answer:
I have opted Kanyakumari in Tamilnadu for this project. It is famous for its sunrise and sunset.

Date/Month	Sunrise	Sunset	Day time Duration	Night time Duration
1/1/2015	06-33	18-13	11-40	12-20
1/2/2015	06-40	18-27	11-47	12-13
1/3/2015	06-33	18-31	11-58	12-02
1/4/2015	06-18	18-29	12-11	11-49
1/5/2015	06-05	18-29	12-24	11-36
1/6/2015	06-01	18-34	12-33	11-27
1/7/2015	06-06	18-41	12-35	11-25
1/8/2015	06-12	18-40	12-28	11-32
1/9/2015	06-12	18-28	12-16	11-44
1/10/2015	06-08	18-11	12-03	11-57
1/11/2015	06-08	17-58	11-50	12-10
1/12/2015	06-18	18-00	11-42	12-18

After thorough observation I came to the following conclusion.
* The duration of night time is more in the months from August to January. The duration of day time is more in the months from February to July.

Question 5.
Explain the idea of rotation of the Earth to your parents or sisters or brothers. Write down their questions or doubts and try to answer them.
Answer:
I explained the earth’s rotation to my brother and sister. I write down their doubts here under.

1. Why does the earth rotate?
2. What is the speed of the earth’s rotation?
3. How can we prove the earth’s rotation?
4. Why is the axis of earth tilled?
5. What happens if earth stops its rotation?

Question 6.
Imagine that the Earth does not rotate but goes around the Sun around the year. What difference will it make to the seasons and distribution of temperature?
Answer:
The one portion of the earth which is infront of the sun would constantly get Sun’s heat and light and the other portion would remain cold and dark. This would make both portions unfit for life-the bright half would be too hot and the dark half would be too cold. This would happen if the earth did not rotate on its own axis.

Question 7.
Identify a country in the Temperate Belt in both Northern and Southern Hemisphere. Compare the seasons in those countries and your place. Which will be warmer in May- June and which will be cooler in December – January or in March or September Identify a country in the Temperate Belt in both Northern and Southern Hemisphere.
(OR)
Compare the seasons in those countries and your place.
Answer:
I have opted Russia in Northern hemisphere, Falkland Islands for this.
Moscow in Russia – It is located near 55.7558° N. latitude. The average temperatures are as follows.

Falkland Islands: It is extended from 51 °S latitude to 52°S. Latitude.

The seasons are quite opposite in both hemispheres.
Ours is Vijayawada in Andhra Pradesh. This is located at 16°5200 N. latitudes. Here April and May are famous for high temperatures. Winter season will be in December and January. When compared to Russia and Falkland Islands, the summer temperatures and winter temperatures are both higher than their summer temperatures. But the seasons in these three areas are more or less equal.

Question 8.
What are the six seasons of Indian climate?
Answer:
The six seasons are:

1. Vasantham – Mid March – Mid May
2. Greeshrnam – Mid May to Mid July
3. Varsha – Mid July to Mid September
4. Sarath – Mid September – Mid November
5. Hemantham – Mid November – Mid. January
6. Sisiram – Mid January – Mid March

Question 9.
Read the first paragraph of this chapter and answer the following question

Human beings live along with a large community of plants and animals. We can observe constant change in the course of the year – the flowering and fruiting of trees and plants changes in the animal activity in our surroundings. As months pass by you would have noticed that trees shed leaves, stand bare, new shoots come forth, they flower and fruit. You may have also noticed that in different times of the year you get different kinds of vegetables and fruits. In some months it is very hot and in some it is cold or wet.

“What is the impact of seasons on the lives of human beings ?”
Answer:
Human beings live along with a large community of plants and animals. We can find a constant change in the course of the year – the flowering and fruiting of trees and plants changes the animal activity in our surroundings. As months pass by, trees shed leaves, stand bare, new shoots come forth, leaves grew again they flower and give fruits. In different times of the year we get different kinds of fruits and vegetables. In some months, it is very hot and in some months, it is cold or wet.

8th Class Social Studies 3rd Lesson Earth Movements and Seasons InText Questions and Answers

Question 1.
Can you relate what are the major seasons you have seen? (Textbook Page No. 33)
Answer:
The major seasons I have seen are Summer season, Rainy season and Winter season.

Question 2.
Can you describe What happen in each -how hot it gets, how much it rains, what happens to the plants and trees and animals, what food you get to eat etc.? (Textbook Page No. 33)
Answer:
Summer season: The atmospheric temperature is too hot i.e., upto 45°C. At the end of this season sometimes it rains. Plants, trees, human beings, animals long for water, food and cool air. This season is famous for watermelons, mangoes and palm fruits etc.

Rainy season: Heavy rains occur during this season. But temperature varies between 30°C to 35°C. We can see greenery everywhere. Cattle are well with their abundant feed. They give us plenty of milk. Many types of vegetables and mushrooms are available.

Winter season: Cold is heavy in this season. Temperature varies from 25°C to 30°C. Even then nights are too cold. Animals also long for warmth. During this season cauliflower, tomato and grapes etc., are available in plenty.

Question 3.
Do you think the trees observed ¡n the pictures are same or different? (Textbook Page No. 33)

Answer:
They are same.

Question 4.
What are the changes you can see in the trees?
Answer:

1. In the first picture it is covered by snow.
2. In the second picture the same tree has fully grown leaves.
3. In the third picture the same tree is sprouting leaves.
4. In the last picture ripe red leaves are falling from the same tree.

Question 5.
Imagine that the Earth goes around the Sun but its axis is not tilted. How will it affect the change in seasons in Andhra Pradesh? (Textbook Page No. 37)
Answer:
This happens if the Earth’s axis is not fitted. Andhra Pradesh is in tropical belt. So the Sun rays fall straight on this area. If the axis is not fitted, there will be continuous temperatures and summer throughout the year on this area. Rainy and winter seasons may not be possible. Most probably the three seasons may come on every day.

Question 6.
How will it affect the change in seasons in the northern region whose photograph you saw in the beginning of the chapter? (Textbook Page No. 37)
Answer:
The photographs are different in different seasons. If the earth’s axis is not tilted, the northern most area on the earth may get freezed. We cannot find any vegetation there.

Question 7.
Find out if there is anyone in the class who has lived in distant places where the seasons are different. Get them to describe what happens there. (Textbook Page No. 33)
Answer:
In my class one student named ‘Atchyut’ came from ‘Dehradun’. He is staying with his grand-parents. His parents are in ‘Dehradun’. He told that the seasons there are entirely different from us. They have heavy winters. Let us listen to his words.
“My name is Atchyut. I came here from ‘Dehradun’ which is at the feet of the ‘Himalayas’. We feel sweat during summer, even though we have less temperatures. Rains are too heavy during the rainy season. Coming to winter season – wow! it is too cold. Hot water should be used for every task in daily life. Warm water is used for drinking. We feel sunlight only after 8 a.m. We must use inners, sweaters, mufflers, caps, socks, and gloves. But our area is very beautiful”.

Question 8.
Find out which country is called the ‘land of midnight Sun’ and locate it on the globe. Find out its latitude and compare it with the latitude of Andhra Pradesh. (Textbook Page No. 34)
Answer:
Norway is called “Land of Midnight Sun. Its latitude is 60.47°N. Some other countries like,

1. Sweden -59.26°N.
2. Iceland – 64.83°N.
3. Lapland -67°N.
4. Denmark – 55.72°N.
5. Finland -62°43″N
6. Alaska -61°18″N
7. Russia – 54°82″N
8. Yukon – 63.63°N
9. Canada – 56°75″ N etc.

comes under this session also. Whereas Latitude as Andhra Pradesh is 80°E;

Question 9.
Look at the globe and find out the names of countries which are located to the south of equator. (Textbook Page No. 34)
Answer:
Asia: Indonesia, partly Maldives partly Sumatra.
Africa: Angola, Botswana, Burundi, South Africa, Tanzania.
Europe: No
North America: No
South America: Argentina, Chile, Bolivia
Australia: Australia, New Guinea

Question 10.
Did you find any continent which is located entirely to the North of the Equator ? (Textbook Page No. 34)
Answer:
Yes. They are Europe and North America.

Question 11.
Did you find any continent which is located entirely to the South of the Equator ? (Textbook Page No. 34)
Answer:
Yes. It is Australia.

Question 12.
Did you find any continent which is spread on both ideas of the North and South of the Equator ? (Textbook Page No. 34)
Answer:
Yes. It is Asia.

Question 13.
Can all the students of the class write down three questions regarding this magic of seasons? we will try to find answers for them. (Textbook Page No. 34)
a) What are the reasons behind the formation of seasons?
Answer:
Earth’s revolution and inclination of the axis are the reasons behind it.

b) In which season the earth tipped towards the sun? (A region)
Answer:
In summer season.

c) What happens if there are no seasons?
Answer:
No seasons, no life on the earth.
Identification of these countries on the globe: Self exercise

Question 14.
Find out if Andhra Pradesh is in the Tropical Belt or in the Temperate Belt. (Textbook Page No. 38)
Answer:
Andhra Pradesh is extended between 12°N to 19°N latitude (approximately). It is in Tropical Belt.

Question 15.
Will the Sun shine directly on our heads in Andhra pradesh during any month? If yes, in which month? (Textbook Page No. 38)
Answer:
The Sun’s rays fall straightly on Andhra Pradesh in the month of May.

Question 16.
Find out in which belt is Delhi and if it will get snowfall in winters. (Textbook Page No. 38)
Answer:
Delhi is located between 28°22″ N. latitude and 28°54″ N. latitude. It is in Temperate Belt. It records low temperatures but there is no snowfall.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 2 Friction Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 2nd Lesson Friction

8th Class Physical Science 2nd Lesson Friction Textbook Questions and Answers

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Question 1.
Do you agree with the statement, “friction is both good and an evil”? Explain with examples.
Answer:
Yes, I agree with the statement friction is both good and an evil.
Explanation with examples.
a) Friction is good:

1. We cannot walk or run without friction.
2. We will not have any cars or bicycles because all of them move because of friction.
3. We cannot stop a moving car by applying brakes.
4. Carpenters will not be able to smoothen surfaces.
5. We will not able to hold any appliances such as hammer, soap, etc.
6. It will not possible to write with pen or pencil if there is no friction.
7. We could not fix nail on the wall.
8. No building could be constructed if there is no friction.

b) Friction is an evil: Friction is undesirable in machinery because it is responsible for overheating and wearing out of moving parts.

Question 2.
Explain why sportsmen use shoes with spikes.
Answer:
The spikes will increases the frictional force so that the sportsmen will get better grip on the floor.

Question 3.
Would it be easier or more difficult for you to walk on soapy water on the marble floor ? Why ?
Answer:
It is more difficult to walk on a marble floor having soapy water because soapy water acts as lubricant and decreases the friction.

Question 4.
What ways do you suggest to reduce friction?
Answer:
Ways of reducing friction:
a) Polishing: Decreasing irregularities of surface (or) smoothening the surface.
B) Lubricants: Using lubricants which will decrease the friction.
c) Ball bearings: Using ball bearings in machinery.
d) Steam lining: Automobiles and aeroplanes are steam lined to reduce the friction due to air.

Question 5.
What conditions are needed for static friction to come into play?
Answer:
The object should be at rest with respect to the surface upto certain limiting acceleration.

Question 6.
Give examples of practical application of static friction.
Answer:
The objects unable to move on their own is due to static friction between surfaces of object.
The practical application of static friction:

1. Construction of buildings.
2. Fixing nail in the wall.
3. A book placed in the shelf unable to change its position because it is unable to overcome frictional force.
4. We can write with pen or pencil due to static friction between finger and pen or pencil.
5. We will not able to hold appliances such as hammer.

Question 7.
Give examples showing the existence of sliding friction.
Answer:

1. A moving ball stops after sometime.
2. If we push an object it will stop after sometime.

Question 8.
Explain how can you measure frictional force?
Answer:
Tie a string around a brick. Pull the brick by a spring balance. When the brick just begins to move note down the reading on the spring balance that measure the force of friction between the surface of brick and the floor.

Question 9.
Explain how does lubrication reduce friction?
Answer:
When oil, grease or any other lubricants are applied between the moving parts of a machine, a thin layer formed between the moving surfaces so they do not directly rub against each other which will avoid the interlocking of irregularities. So lubrication reduce the friction.

Question 10.
What kinds of friction do you know?
Answer:
There are three types of friction.

1. Static friction
2. Sliding friction
3. Rolling friction

Question 11.
Explain why sliding friction is less than static friction.
Answer:
When an object starts sliding, the contact points on its surface do not get enough time to lock into the contact points on the floor. So the sliding friction is slightly less than the static friction.

Question 12.
Give examples of how is friction responsible for energy wastages? Give suggestions to reduce energy wastages by friction.
(OR)
How is friction responsible for energy loses give examples? Give suggestions to reduce energy loses by friction.
Answer:
As the friction increases the machinery parts develops heat there by efficiency of the machine decreases which leads lot of wastage of energy. The wastage of energy is due to overheating and wearing out of moving parts.
Suggestions:

1. To reduce friction between rotating shafts of machine tools we should have to use ball bearings.
2. Replacing wearing out of moving parts with new ones.

Question 13.
Seetha is observing a moving bus with the luggage on its top. As the bus is moving slowly there is change in the state of luggage on its top. But when the bus speeds up and starts moving fast, she noticed that the luggage on the top of the bus fell to the back of the bus. This raised many doubts in her mind regarding to the effect frictional force acting on the luggage as well as on the tyres of the bus. Can you guess the questions raised in her mind ? Write them.
Answer:

1. Why the bag is moving backward direction?
2. In which direction friction is acting on the bus as well as on the bag?
3. Whether frictional force effecting relative motion between bag and bus?
4. What happens to frictional force if we replace bag with other object?

Question 14.
Collect information either from internet or from books in library, about various new techniques being adopted by human beings to reduce energy losses due to friction. Prepare a note on that.
Answer:

1. We are using grease, oil, wax and other lubricants in the vehicles and machinery to reduce the friction.
2. Ball bearings are also used to reduce the friction.
3. Engine oil, gear oil, brake oil, clutch oil, etc. are used in vehicles.
4. Shock up oil is also used.
5. Levers are reducing the friction.
6. In trolleys and other vehicles which should carry heavy loads, the wheels are fixed.

Question 15.
Draw a free body diagram (FBD) to show various forces acting on a body which is sliding on an inclined plane.
Answer:

Question 16.
“Reducing friction to the lowest possible level in machine tools solves the problem of energy crisis and conserve biodiversity”. How do you support the statement? Explain.
Answer:
Yes, it will solve the problem of energy crisis and conserve biodiversity the reason is the majority of energy wasted in the form of heat energy due to friction. In order to develop more electrical energy we are depending on coal, petroleum, gas, nuclear energy and hydro electricity. The production of energy from these sources except hydroelectric power causing severe air pollution which are affecting animals and plants. So energy should be conserved by means of reducing friction.

8th Class Physical Science 2nd Lesson Friction InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 22

Question 1.
Does friction oppose motion or relative motion of surfaces in contact? Discuss.
Answer:
Yes. Frictional force opposition or relative motion of surfaces in contact that’s why an object placed on a table unable to move on its own because it is unable to overcome friction similarly a moving ball comes to rest after sometime due to friction.

Question 2.
What observations and experiments can you cite to show the existence of friction?
Answer:

1. Push a ball on a sandy surface and on a concrete surface and the observation is on a concrete surface it travels more distance, the reason is the concrete surface apply less frictional force on the ball.
2. Apply vehicle brakes during summer and rainy seasons and the observation is during summer season the brakes works more efficiently than rainy season the reason is friction between tyre and brakes is less because rainy water acts as lubricant.

Question 3.
When do we speak of sliding friction?
Answer:
When applied force is more than the limit of static friction, the body starts to move then we speak about sliding friction.

8th Class Physical Science Textbook Page No. 25

Question 4.
Does friction act on a table resting on the floor?
Answer:
Yes, frictional force is acting on the table which is known as static friction.

Question 5.
If normal force is doubled ? What happens to friction? Discuss.
Answer:
Friction is directly proportional to normal force therefore friction will be doubled if the normal force is doubled.

Question 6.
Your friend says “friction depends on the area of contact?” How do you correct your friend through some experiments ?
Answer:
If is plain that the friction doesn’t depend on area of contact, I will explain this fact to my friend by fastening a brick kept horizontal to the surface to a spring balance and pulling it at the hook. The same experiment I do by keeping the brick vertical to the surface. In both the experiments we find no difference and I will make him to come to the conclusion that the friction depends on the normal force and not on weight of the object on the surface of contact.

Question 7.
“Friction is independent of weight, but depends on normal force between surfaces of contact where friction exists.” Do you agree with this statement? Discuss.
Answer:
Yes, I agree with this statement. The above experiment helps us to come to this conclusion. In both cases we used the same brick hence the weight doesn’t change. But when its positions were changed the frictions at each case is changed.

8th Class Physical Science Textbook Page No. 26

Question 8.
What important role does friction play in the life of human beings and animals?
Answer:

1. Without friction human beings and animals unable to walk or run on any surface.
2. Without friction they unable to hold any appliances.
3. It will not be possible to write with pen or pencil if there is no friction.
4. We cannot stop car or cycle by applying brakes.
5. No building is constructed if there is no friction.
6. Carpenters will not be able to smoothen surfaces.

Question 9.
Why is friction important for transport?
Answer:
Threading in tyres provide friction for cars or buses so that they can move safely therefore friction is important for transport.

8th Class Physical Science Textbook Page No. 28

Question 10.
Can we reduce friction to zero? Explain.
Answer:
No, we cannot. Friction can never be entirely eliminated because no surface is perfectly smooth and some irregularities are always there.

Question 11.
What purposes are served by bearings in machines? Explain with daily life situations.
Answer:
The ball bearings are used to reduce friction between rotating shafts of machine tools and it increases the efficiency of machines.

8th Class Physical Science 2nd Lesson Friction Activities

Activity – 1
Question 1.
Identifying forces acting on a body and effect of frictional force.
Gently push a book on a horizontal floor. You may observe that the book acquires certain speed in the direction of push. However, the speed of the book gradually decreases and after sometime it stops.

a) Why does the book stop after covering some distance?
Answer:
Some opposing force is acting to its motion.

b) Is the book moving with uniform speed?
Answer:
No, its speed decreases gradually.

c) Why does the speed of the book change gradually?
Answer:
Some net force is acting opposite direction to its motion.

d) How many forces act on the book when it is pushed on the floor?
Answer:
Two forces act on the vertical direction. They are

1. Weight of the book or gravitational force acting vertically down.
2. Normal force or reaction force applied by the floor vertically up.
3. Forces acting horizontal direction.

e) What are the forces acting on the book in the horizontal direction?
Answer:

1. Muscular force applied by us.
2. Opposing force acting opposite to motion of book.

f) What is the net force acting in the horizontal direction?
Answer:
The net force is the difference between muscular force and opposing force to the motion of book.

Lab Activity

Write an activity to understand friction and static friction.
(OR)
Conduct an experiment to understand the nature of friction and the concept of static friction.
Answer:
Aim: To understand the nature of friction and the concept of static friction.
Materials required: Toy trolley, small wooden block, inextensible string, weight hanger, weights, pulley and table.
Procedure: Take a small toy trolley and keep a small wooden block on it as in the figure. Tie an inextensible string to the trolley and pass it over a pulley. And other end of the string is fixed to weight hanger. Take a small weight and keep it on weight hanger and observe the changes in motions of block and trolley.

Observation:
The trolley with block moves towards left with an acceleration. The block is not with respect to the surface of trolley, but it is in motion with respect to surface e table. The force of friction of the trolley acts on the direction of motion.
We increase trolley’s acceleration gradually by increasing the weight on the hanger at certain limiting weight the block comes in motion in the reverse direction.
That means now there exists relative motion between the surface of the trolley and block.
Result:
The force which opposes the relative motion of the two surfaces of bodies which are in contact is called frictional force.
The block is at rest relative to surface of the trolley upto a certain limiting acceleration. The friction exists at that stage is called static friction.

Activity – 2

Question 2.
Observing the variation of friction.
Push a heavy box which is kept on a floor. The box does not move. Now increase the applied force until the box moves.

a) Why does the box does not move at first?
Answer:
The applied force is less than frictional force (static friction).

b) When does the box tends to move?
Answer:
When the applied force is more than static friction.

Activity – 3

Question 3.
Effect of roughness on frictional force.
Set up an inclined plane on the horizontal floor. Use a wooden board as inclined plane. Put a mark at any point
‘A’. Now let a pencil cell or ball is move down from this point. Note down the distance travelled by the ball from the bottom of the inclined plane to point where it comes to a stop.

Now, spread a cloth over the floor. Try again with ball and note down the distance.

a) What are your observations from these experiments?
Answer:
The distance covered by ball in the two cases are different.

b) In which case is the distance covered maximum?
Answer:
When there is no cloth on the floor.

c) In which case is the distance covered minimum?
Answer:
When cloth is spread over the floor.

d) Why is the distance covered by the pencil cell different on different surfaces?
Answer:
Because, the friction offered by different surfaces are different.

e) If the cloth is replaced with white marble surface or glass surface, what will be your prediction about the distance covered by the pencil cell?
Answer:
The pencil cell covers more distance.

Activity – 4

Question 4.
Effect of area of contact on frictional force.
Tie a string around a wooden block and pull the wooden block by using a spring balance.

Pull it to make a move in the brick. Note down the readings of spring balance when the brick just begins to move.
a) How many forces are acting on the wooden block in the horizontal direction?
Answer:
Two forces are acting in the horizontal direction.

1. Force of friction,
2. Force applied by us.

Now turn the wooden block upright and measure the friction by doing the same experiment using the reading of the spring balance.

b) How does the frictional force vary with the change in the area of contact?
Answer:

The frictional force appears the same in both cases irrespective of area of contact. So it is independent of area of contact.

Activity – 5

Question 5.
Effect of normal force on friction.
Keep a wooden block on the horizontal floor and pull it with the spring balance attached to it and measure the frictional force.
Now put another wooden block over the brick tied to the spring balance or press it vertically with your hand and measure the frictional force.
a) Is there any difference between frictional forces in two cases? If yes, why?
Answer:
Yes, the reason is when we add a wooden block to the existing wooden block or apply force by pressing vertically, the normal force increases and hence we find increase in frictional force.

b) What is the relationship between friction and normal force?
Answer:
Friction is proportional to the normal force, i.e., friction °c normal force.

Activity – 6

Question 6.
Friction produces heat.
a) Rub your palms against each other for a few minutes. How do you feel?
Answer:

They became hot.

b) Strike a match stick against the rough surface of match box. What happens?
Answer:
The match stick catches fire.

c) What is your observation in this activity?
Answer:
Temperature of surfaces increases due to friction.

d) What is your conclusion on this activity?
Answer:
Friction can also produce heat.

e) You have probably heard that space craft returning to the earth have to be protected by a heat shield covering it. Find out why. What is the material used as heat shield?
Answer:

Space craft returning earth have to be protected by a heat shield covering it in order to protect it from atmospheric friction.
The material generally used is insulator of heat.

Activity – 7

Question 7.
How to increase Motion?
Take a spoon and hold its head (broader portion) in the left hand and hold the mid portion of the spoon by the right hand and pull it towards the other end of the spoon.
a) What do you notice?
Answer:
We unable to pull the spoon.
Now dip your right hand fingers in water, do it again as said above.

b) In which case is it easy to pull? Why?
Answer:
In second case it is easy to pull because water decreases the friction.

c) Have you ever thought why the sole of your shoes is grooved as shown in figure?
Answer:

It will provide shoes better grip on the floor so that we can move safely.

d) Cars, trucks and bulldozers tyres are threaded. Why?
Answer:

To provide them better grip on the floor.

e) Why do you need to change the tyres when it’s threading is worn out?
Answer:
If we does not change the tyre then the frictional force decreases and the vehicle may skid.
Play carrom board without powder and then play with fine powder sprinkled on board.

f) In which case is the movement of the striker and the coins easy? Why?
Answer:
When fine powder sprinkled on board, it will decrease the friction between coin and board surface.

g) Why do we pour a few drops of oil on the hinges of a door?
Answer:
It will decrease the friction and provide better movement of door.

h) Why do we use grease between the moving parts of motor vehicles?
Answer:
To reduce friction in order to increase efficiency.

Activity – 8

Question 8.
Effect of rollers on friction.
Pull a suitcase without rollers and pull a suitcase which has rollers.

a) In which case is the pulling easy? Why?
Answer:
It is easy to pull when suitcase has rollers.
Try to push a book lying on the table. Now place the book on two to three pencils or pens without caps. Push the book again.

b) What do you notice ? In which case is it easy to pull the book? Why?
Answer:

In the second case it is easy to pull the book. The reason is it is always easier to roll a body than to slide it over a surface.

Activity – 9

Question 9.
Understanding the principle of ball bearings.
Take two lids and rotate them by putting one on the top of the other.

a) What do you observe?
Answer:
It is difficult to rotate them.
Now place three to four marbles on one lid and place the other lid on the top of the marble. Now try to rotate the top lid.

b) What do you observe?
Answer:
Now we can easily rotate the lid because rolling friction is less than sliding friction.

c) What is your conclusion on the principle of ball bearings?
Answer:
We can easily rotate top lid by placing marbles between the lids. This is the principle of ball bearings.

Activity – 10

Question 10.
Observing fluid friction.
Take a glass of water and stir it with a spoon. You know that water whirls around an axis. Stop stirring and see what happens.

The whirling speed of water gradually decreases and after some – time, the water stops whirling and comes to a stable state

a) Which force is responsible for stopping the rotation of the water.
Answer:
The frictional forces between the liquid layers or between the liquid surfaces that is in contact with glass surface.

Activity – 11

Question 11.
Identifying factors influencing the fluid friction.
Take a tub of water. Try to move your hand in water in the direction of stretched fingers i.e., up and down. Now try to move your hand in the direction perpendicular to the plane of the hand i.e., to and fro.

a) In which orientation of your hand, do you experience more drag? Why?
Answer:
We experience more drag in the direction of stretched fingers. The frictional force on an object in a fluid depends on its speed with respect to fluid and on the shape of the object and nature of the fluid.
When objects move through fluids, they have to overcome friction acting on them. So objects are given special shapes to minimise fluid friction.

b) Where do you think scientists get hint for these special shapes?
Answer:
From nature i.e., from birds and fishes, which have to move about in fluids all the time.

c) Do you find any similarity in the shape of an aeroplane and a bird? Why?
Answer:
Yes. The shape of aeroplane designed as bird in order to reduce fluid friction.

AP State Syllabus AP Board 8th Class Social Studies Important Questions Chapter 13 The Indian Constitution.

AP State Syllabus 8th Class Social Studies Important Questions 13th Lesson The Indian Constitution

Question 1.
Write some of the inequalities prevalent in our society at the time of Independence.
Answer:

1. Economic inequalities
2. Social inequalities

Question 2.
Write some of the discriminations prevalent in our society at the time of Independence.
Answer:

1. Racial discrimination
2. Gender discrimination

Question 3.
“A Constitution is a set of rule. ” Write any two rules.
Answer:

1. How the country should be governed,
2. How the government should be formed.

Question 4.
Why do you think the kings were allowed to nominate members to the Constitutent Assembly?
Answer:
The kings were familiar with the ideas of their people. They could integrate the ideas of their people. So the kings were allowed to nominate members to the Constituent Assembly.

Question 5.
Why do you think there were so few women members? Do you think it would have been better if there had been more women members?
Answer:
At that time the educated women and the women politicians were very less in number. Even today we are fighting for 33% of women reservations. So there were so few women members. Yes, I think it would have been better if there had been more women members.

Question 6.
Which of the guiding principles in the Objective Resolution, do you think is the most important?
Answer:
“Welfare of all mankind” – This guiding principle in the Objective Resolution is the most important.

Question 7.
Why is it necessary for an elected parliament to make laws?
Answer:
Our constitution provides us a parliamentary form of government. The Parliament, consisting of representatives of the people makes laws. These laws are according to the needs and views of the citizens/people. Judiciary comments on this.

Question 8.
Why do you think the Prime Minister and his Cabinet should get their decisions and actions approved by the Parliament and answer the questions raised by the members of Parliament?
Answer:
The Prime Minister and the Cabinet are answerable to the Parliament. The members of Parliament are the representatives elected by the civilians directly. So they are answerable to them.

Question 9.
Some countries have a different structure, in which there is only a central government which makes laws for the entire country and governs all the provinces or states. Do you think such a system is suited for India?
Answer:
India is a land of many diversities. Different regions have different cultures. All these things should be taken into consideration to make laws. So such system is not suited for India.

Question 10.
Discuss why the courts and judges should be independent of the state and central government authorities.
Answer:
To safeguard the Constitution, the courts and judges should be independent. Otherwise there is a chance of sidetrack. So they should be independent.

Question 11.
Why should the Election Commission be autonomous?
Answer:
The Election Commission should be autonomous to conduct free and fair elections.

Question 12.
Read the section ‘Dream and Promise’ again. Draw a table with statements that you consider as dream in the first column and promise in second column.
Answer:

Dream	Promise
1) Release India from all thraldom and patronage.	1) No room for the curse of untouchability.
2) Land of no classes.	2) Or the curse of intoxicating drinks and drugs.
3) Perfect harmony.	3) Women will enjoy the same rights as men.
4) One man, one vote and one vote, one value.	4) Political equality.
5) Service of India, never ending work.	5) The ending of inequalities, to wipe every tear from every eye.

Question 13.
Observe the following picture and write your comments.

Answer:
This picture belongs to the celebrations of 26th January, the Republic Day. These are NCC students/cadets. They are marching in daylight without gender discrimination. Their faces are bright with self-reliance.

Question 14.
Match the names of the leaders with their photos.

Answer:
1) D,
2) C,
3) A,
4) B

Question 15.
Which aspects of the dreams and promises can you identify in the words used in preamble? Create a chart to show the relationships.
Answer:

Question 16.
Read the following passage.
When India gained its freedom from colonial rule it was decided to put together basic principles for which we stood and principles and procedures by which our country would be ruled. These were written down in a book called the ‘Constitution of India’.

A Constitution is a set of rules about how the country should be governed- how the laws that run it would be made or changed, how the government should be formed, what would be the role of the citizens, what would be their rights, etc. Above all, the Constitution sets before the country the goals for which the country has to strive.

Now answer the following questions:
1. From whom did India gain freedom?
Answer:
India gained its freedom from colonial rule.

2. Where were the basic principles and procedures written?
Answer:
These were written in a book called The Indian Constitution’.

3. “A Constitution is a set of rule.” Write any two rules.
Answer:

1. How the country should be governed?
2. How the government should be formed?

4. Above all the Constitution sets before the country ———– the for which the has to strive.
Answer:
goals.

Question 17.
Read the following passages.

Some of you may have noticed a name missing from the sketches of the makers of the Constitution: Mahatma Gandhi. He was not a member of the Constituent Assembly. Yet there were many members who followed his vision. Writing in the magazine Young India in 1931, he had spelt out what he wanted the Constitution to do:
I shall strive for a Constitution which will release India from all thraldom and patronage… I shall work for an India in which the poorest shall feel that it is their country in whose making they have an effective voice; an India in which there shall be no high class and low class of people; an India in which all communities shall live in perfect harmony. There can be no room in such an India for the curse of untouchability or the curse of the intoxicating drinks and drugs. Women will enjoy the same rights as men… I shall be satisfied with nothing else. – Mahatma Gandhi
Now answer the following questions :
1. Whose name was missing from the sketches of the making of the Constitution?
Answer:
The sketch of Mahatma Gandhi.

2. Where was the dream written?
Answer:
In a magazine called ‘Young India’.

3. Whose dream was this?
Answer:
This was the dream of Mahatma Gandhiji.

4. There can be no room in such an India for the curse of ———–, ———– and ———–.
Answer:
Untouchability, drinks, drugs

5. ———– will enjoy the same rights as men.
Answer:
Women.

Question 18.
Locate the following in the given World map.

1. India
2. South Africa
3. U.S.A.

Answer:

AP State Syllabus AP Board 8th Class Biology Solutions Chapter 3 Story of Microorganisms 2 Textbook Questions and Answers.

AP State Syllabus 8th Class Biology Solutions 3rd Lesson Story of Microorganisms 2

8th Class Biology 3rd Lesson Story of Microorganisms 2 Textbook Questions and Answers

Improve Your Learning

Question 1.
How do vaccines works in our body?
Answer:
When a vaccine is given which contains weak microorganisms our body learn to fight them by producing antibodies whenever danger comes. When the disease causing microorganisms enter in our body, the already present antibodies fight and eliminate them. And the disease is controlled. The weakened disease causing microorganisms which are injected into our bodies are called as vaccine.

Question 2.
What are the differences between Antibiotic and Vaccine?
Answer:

Antibiotic	Vaccine
An antibiotic is a compound or a substance that inhibits or kills the growth of bacteria.	Vaccine is a preparation that improves the immunity to a particular disease.
An antibiotic heals infection caused by small pox.	A vaccine prevents diseases like polio, bacteria.
Antibiotics are available in different forms like tablets, capsules, drops or ointments.	Vaccines can be given orally or through injection.
Antibiotics are taken after getting infected.	Vaccines are preventive method that is taken before getting infected.

Question 3.
Invention of pencillin protected the world from deaths during first world war, Explain.
Answer:

1. Pencillin was invented by Dr. Alexander Flemming.
2. He was an army doctor in First World War.
3. In the First World War many injured soliders died because of bacterial infection of wounds.
4. Pencillin killed many disease causing bacteria.
5. So the invention of pencillin protect the world from deaths during the first World War.

Question 4.
Take three bowls and mark as A,B,C. Pour lukewarm milk in bowl A, hot milk in bowl B, cold milk in bowl C. Add one tea spoon of curd or butter milk in three bowls and stir them slightly. Cover the bowls with lids. Keep the bowls undisturbed for five to six hours. In which bowl milk turned into curd ? Give your reasons.
Answer:
After six hours the milk in the bowl A converted into curd.
This conversion is happened by fermentation. Fermentaion is one kind of enzy-matic action in anaerobic respiration. Fermentation needs the help of microbes like yeast or some other bacteria. This process occurs at a particular temperature. Be-cause of enzymes are inactive at low and high temperatures. Hence the milk in bowl A converted into curd by the bacterium Lactobacillus.

Question 5.
Collect more information about scientists who invented and discovered other facts related to Microorganisms. How these discoveries helped mankind ? Make a chart presentation and paste it on your classroom wall magazine.
Answer:

Question 6.
Make an album of scientists and their discoveries related to Microorganisms.
Answer:

Question 7.
Visit the veterinary hospital and prepare a list of cattle diseases by asking questions, to the doctor.
Answer:

Disease	Animal
1) African Horse Sickness	Horses
2) Bovine Spongiform Encephalopathy	Cattle
3) Contagious Equine Metritis	Horses
4) Equine Infectious Anaemia	Horses
5) Anthrax	Cattle and other mammals
6) Brucellosis (Brucella abortus)	Cattle
7) Brucellosis (Brucella melitensis)	Sheep and Goats
8) Contagious agalactia	Sheep and Goats
9) Contagious bovine pleuro – pneumonia	Cattle
10) Dourine	Horses
11) European Bat Lyssavirus (FBLV)	Bats
12) Enzootic bovine leukosis	Cattle

Question 8.
What is pasteurisation? What is the use of it?
Answer:

1. Pasteurisation is a process which helps in the preservation of the milk.
2. It is discovered by “Louis Pasteur.” Hence it is called as pasteurisation.
3. In this process milk is heated up to 70° for 15 to 30 seconds and suddenly chilled and stored.
4. This prevents the growth of the microorganisms.

Question 9.
How do you appreciate Edward Jenner’s experiment?
Answer:

Edward Jenner was a man of the Enlightenment and believed in the intellectual and moral improvement of mankind.
Possessing that spirit, he predicted in 1801 that “the annihilation of small pox-the most dreadful scourge of the human race-will be the final result of this practice” of vaccination. And he was right. Since the Enlightenment, the core branches of science and medicine have generally developed rationally. As a result, the World Health Organization was able to declare in 1980 that smallpox had been eradicated worldwide. Only two laboratory samples emained, one in Russia and one in the United States.

Question 10.
Visit a nearby milk chilling centre. Observe the process and make a report on it.
Answer:
The Milk Collection Station is a specially designed, integrated unit, which combines the several functions of a milk collection centre. It measures the weight, fat content and gives the price of the milk brought in by the each producer. The equipment is particularly useful for the milk cooperatives / milk collection centres as it can also maintain a summary of milk supplied. This state of the art equipment operates both on battery and mains and is able to process and record 120-150 milk collection per hour. An Electronic Milk Weighing Unit, the Electronic Milk Tester and Data Processor Unit are main components of the system. The membership code of individual mem¬bers is entered automatically by member identity card / manually by an electronic key-board.

Question 11.
“Prevention is better than cure” comment.
Answer:
We heard about “prevention is better than cure” since our childhood – brushing of teeth twice to prevent tooth decay, washing of hands before eating to prevent stomach upset, do not eat uncovered road side food items, get vaccine against polio to free from disability, get rid of stagnate water to prevent malaria like that follow the life skills to avoid dangerous AIDS. It’s better to take care that a problem does not happen than to have to solve the problem afterwards. It’s easier to stop something bad from happening in the first place than to fix the damage after it has happened.

Question 12.
Raheem tells to his neighbours, “stagnation of’ sewage in our surroundings is harmful to our health. ” Do you support this? Why?
Answer:
Stagnation of sewage in our surroundings is harmful to our health in different ways. Sewage consist different wastes of organic matters. Microbes decompose all organic wastes. Disease transmitting carriers prefer to grow on decomposing organic matters. Hence sewage provides good shelter to mosquitoes, houseflies and other insects which transmit life threatening diseases like encephalitis, malaria, cholera, typhoid and other epidemics. Therefore sewage stagnation is more harmful to our health.

Question 13.
Jeevan said that “If there are no microorganisms earth will remain with wastes. ” Will you agree this statement? Why?
Answer:
Yes, I will agree this statement. Because of:

1. Microorganisms present in the soil, air and water act upon wastes around us.
2. They decomposes them.
3. They are converted into simple substances.
4. Thus microorganisms help us in cleaning the environment.
5. So if there are no microorganisms earth will remain with wastes.

Question 14.
Pranavi is suffering from serious illness. Doctor prescribed antibiotics for five days. After three days of usage she stopped taking antibiotics. Is it right or not, discuss.
Answer:
No, it is not right. Doctor prescribed anitbiotics for five days. Because the doctor knows that the correct days of the recovering of her illness. After three days of usage she stopped taking antibiotics. But her illness is not completely recovered. It is breaking out after some time. So it is not right.

Question 15.
What are the precautions taken to eradicate malaria?
Answer:

1. Malaria is caused by the pathogen piasmodium, is transmitted by female Anopheles mosquito.
   
2. Methods used to prevent malaria include medications, mosquito elimination and the prevention of bites.
3. Using of indoor mosquito repellents, residual sprays, taking care not to store water.
4. Providing awareness how to control mosquito population.

Question 16.
One medical store owner is giving antibiotics to his customer who is suffering from fever without doctor’s prescription? But the customer’s daughter Malathi is telling her father not to take antibiotics without doctor’s prescription. Whom do you support and why?
Answer:
We must use antibiotics prescribed by qualified doctor only. If you use antibiotics without consulting a qualified doctor it may harm us. Unnecessary use of antibiotics affects blood cells which fight infections. Sometimes they may kill useful bacteria too in our intestine and this increases the resistance towards antibiotics.

8th Class Biology 3rd Lesson Story of Microorganisms 2 InText Questions and Answers

Question 1.
What diseases can be prevented if we control mosquitoes?
Answer:
Malaria, Dengue, Chickungunya, Japanese Encephalitis.

Question 2.
Which diseases can we prevented by vaccination?
Answer:
Tuberculosis, Chickenpox, Measles, Polio, Swineflu.

Question 3.
Name the diseases which are transmitted by contaminated water?
Answer:
Cholera, Typhoid

Question 4.
Can you name some diseases which are transmited by Air?
Answer:
Tuberculosis, Chickenpox, Measles, Polio, Swineflu.

8th Class Biology 3rd Lesson Story of Microorganisms 2 Activities

Activity – 1

Question 1.
Take some lukewarm milk in two small bowls. Add a few drops of butter milk or little curd in one of the bowls. In the second bowl do not add anything. Keep the two bowls in a warm place and observe the milk in the bowls after 5 to 6 hours.
a) What changes did you observe?
Answer:
In the first bowl milk changed into curd. There is no change in the second bowl.
b) What is the reason for this?
Answer:
We add curd or butter milk in the first bowl. Curd or buttermilk contain bacterium named lactobacillus. Lactobacillus converts the milk into curd.

Activity – 2

Question 2.
Take 100 grams of maida in a bowl, add one or two spoons of yeast powder, add some water and knead it to make dough. Keep the dough in a warm place. Observe the dough after 3 – 4 hours.
a) What changes do you observe in the dough ?
Answer:
We observe that the dough rises and increase its volume.
b) What might be the reason ? Discuss with your friends and write about it.
Answer:
When yeast is added to the maida dough, the dough rises. This is due to the produc¬tion of carbondioxide gas during the process of fermentation. Bubbles of the gas fill the dough, increase its volume and make it spongy in nature.

Activity – 3

Question 3.
Commercial use of microorganisms.
Take some water in two separate beakers. Add 5 to 10 spoons of sugar to each beaker, then add 2 to 3 spoons of yeast to one of the bowls only. Close both of the bowls with lids and keep them in a warmplace. After 3 to 4 hours remove the lids and smell the contents.
a) What differences did you observe between the two bowls?
Answer:
We feel a new variety of smell from one of the bowls. This is the characteristic smell of alcohol. There is no smell from another bowl.
b) What will be the reason for the odour in yeast mixed bowl?
Answer:
Sugars are converted into alcohol by yeast. This process of conversion of sugars into alcohol is known as fermentation.

Activity – 4

Question 4.
Visit nearby PHC and collect information about vaccination given to 0-15 years chil-dren. Meet a doctor or a health worker and ask what types of vaccines are there ? Which disease can be prevented ? When it should be taken? List them out.
Answer:

Activity – 5

Question 5.
Take two pots or dig two pits in the corner of the garden at home or at your school ground. Fill them up to half with loose soil. Put some biological wastes like fallen leaves, vegetable wastes, waste papers, etc., in one of them. Fill the second one with plastic wastes, polythene bags and with some empty glass bottles.
Answer:
Now cover both the pits with soil and sprinkle water twice a day up to three weeks and observe the changes in both the pits and record.
After three weeks the pit which consists organic wastes decomposed into inorganic matter. But the pit which is filled with polythene bags, plastics and glass bottles is remain same no change is observed. Because of plastics and polythene materials are non biodegradables.

Activity – 6

Question 6.
Meet a doctor of your locality and ask him about the different types of diseases, caused by different microorganisms. Note them down. (OR)
Read the following table and answer the following questions.


Questions:
a) Name the viral diseases that can be prevented by controlling mosquito population.
Answer:
Dengue, Chikungunya, Japanese encephalitis.

b) Which bacterial disease / diseases cannot be controlled by vaccination (acc.to above table) ?
Answer:
Cholera, Typhoid.

c) What would you do to control mosquito population ?
Answer:
Use mosquito repellents, control breeding of mosquitoes by not allowing water stag¬nation in our surroundings.

d) Name the viral disease that spreads through water.
Answer:
Polio.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 5 Metals and Non-Metals Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 5th Lesson Metals and Non-Metals

8th Class Physical Science 5th Lesson Metals and Non-Metals Textbook Questions and Answers

Improve Your Learning

Question 1.
Explain the physical properties of metals with suitable examples.
(OR)
Explain briefly the physical properties of metals.
Answer:
Physical properties of metals:

1. Lustrous:
   When we rub the surface of metals with sand paper they will shine. This property is called lustrous, e.g.: Iron, zinc etc.
2. Sonority:
   When we hit the metal surface they give a ringing sound is called sonority, e.g.: Iron, copper etc.
3. Malleability:
   Metals can be flattened into thin sheets. The property of flattening metals into thin sheets is called malleability, e.g.: Silver, Iron, copper.
4. Ductility:
   Metals can be drawn into wires.
   The property of drawing a metal to make fine wire is called ductility, e.g.: Silver, gold.
5. Electric conductivity:
   Electricity can be easily pass through metals. So they are called good conductors of electricity.
   e.g.: Silver, copper, iron.
6. Conductivity of heat:
   Metal absorbs heat quite easily. They are good conductors of heat, e.g.: Copper, iron.

Question 2.
You are given two samples. How do you distinguish which is metal and which is non-metal?
Answer:

1. By physical properties, generally we can judge whether the given sample is metal or non-metal that is metals are hard. They are lustrous, sonorous, malleable, ductile and good conductors of heat and electricity.
2. Generally metal sample react with water and non-metal sample does not react with water.
3. Generally metal sample react with acid and produce hydrogen gas whereas non-metal samples does not react with acid.

Question 3.
Which metals are used in making jewellery? Why?
Answer:
Generally we use metals like gold, silver and copper for making jewellery due to their high ductility and lustrous surface.

Question 4.
Which substance liberate hydrogen when react with metals?
Answer:
Generally acids react with metals and liberate hydrogen gas. Water also react with some metals and liberate hydrogen gas.

Question 5.
In a chemical reaction iron is unable to displace zinc from zinc sulphate. Why?
Answer:
Zinc is more reactive than iron. A less reactive metal cannot displace a more reactive metal from its salt solution. So iron unable to displace zinc from zinc sulphate.

Question 6.
Why cooking pans do not have metal handles?
Answer:
Metals are good conductors of heat. So they gain heat easily. So in order to avoid the burning of our palms, the handles of cooking pans made of heat resist material such as plastic.

Question 7.
Sulphur dioxide is
A) basic oxide
B) acidic oxide
C) neutral oxide
D) amphoteric oxide
Answer:
B) acidic oxide

Question 8.
Match the following.
Group – A                                             Group – B
1. Making into thin sheets        ( )        A) Ductility
2. Shining materials                  ( )        B) Conductivity
3. Making into wires                 ( )        C) Sonority
4. Transmission of heat            ( )        D) Lustrous
5. Making ringing sound          ( )         E) Malleability
Answer:
1. E
2. D
3. A
4. B
5. C

Question 9.
Which gas makes a ‘pop’ sound if exposed to lighted matchstick?
Answer:
Hydrogen gas makes a pop sound when it is exposed to a lighted matchstick.

Question 10.
Why are bells made up of metals instead of wood
Answer:
Metals have sonority property that means they make ringing sound when we hit them with a hammer. Where wood does not give ringing sound when it is hit with a hammer. So bells are made up of metals instead of wood.

Question 11.
Imagine the human life without metals, write briefly about the consequences.
Answer:

1. There would not be any utensil for cooking.
2. There would not be trains, buses, aeroplanes for travelling.
3. There would be no almirahs, no school bells, no agricultural material, no electrical appliances, no automobiles, no satellites, no machinery and no decorative material. So everything in life directly or indirectly depends upon metals. So we cannot imagine a life without metals.

Question 12.
After completion of metals and non-metals chapter, Raheem understood that metals are hard and non-metals are soft. During the discussion with his brother he came to know that diamond is a hardest material and it is a non-metal. Similarly mercury is a soft material and it is a metal. These findings from the discussion raised some questions in Raheem’s mind. Can you guess those questions? Write them.
Answer:
The doubts arised in Raheem’s mind are

1. If diamond is hard how it behaves like a non-metal?
2. If mercury is soft material how it acts as metal?
3. What are the properties which actually decide whether the given material is either metal or non-metal?

Question 13.
Discuss the acidic and basic nature of the metals and non-metals with suitable experiments.
Answer:
Take a small strip of magnesium and burn it. It forms white ashes of magnesium oxide collect the ashes of magnesium and add some distilled water to it. Test the solution with red and blue litmus papers. Note the colour changes. The solution turns red litmus into blue. It indicates given solution is basic. So metallic oxides are basic in nature.
Take a small amount of powdered sulphur in a deflagrating spoon and heat it. As soon as sulphur starts burning, introduce the spoon into a gas jar or tumbler. Cover the tumbler with lid to ensure that the gas produced does not escape. The gas formed is sulphur dioxide. Remove the spoon after some time but try to keep the jar covered. Add a small quantity of water into the tumbler and quickly replace the lid. Shake the tumbler well. Check the solution with red and blue litmus paper. The solution turns blue litmus into red. It indicates the solution is acidic. So non-metallic oxides are acidic in nature.

Question 14.
How do you appreciate wide range utility of aluminium right from utensils to space craft?
Answer:
Aluminium is essential part of our life. Aluminium foil is used on inner packing of food materials and toffees. Aluminium and copper mixture is used in currency coins, medals and statues. Aluminium is used in electrical appliances, automobiles, satellites, space crafts, aeroplanes, cooking utensils, machinery, decorative materials. This indicates wherever we go we observe articles made up of aluminium. So we require aluminium for better living.

Question 15.
How is malleability of metals used in our daily life
Answer:
Metals can be flattened into sheets is called malleability. Due to this metals can be made into different shapes like railway coaches, railway tracks, cooking utensils, etc. So malleability of metals is extremely useful in daily life.

Question 16.
Dumping of waste material made up of metals and non-metals leads to environment pollution. Do you support the statement? Give your justification with suitable examples.
Answer:
Soil samples analyzed from location adjacent and with in deposite show high level of heavy metals in particular lead, mercury, cadmium, copper and chromium. In which lead and mercury are extremely harmful to environment as well as mankind. After medical evaluation the adolescents living and children living near dump site had high incidence of diseases that are associated with high exposure levels to these metal pollutants. So waste material made of metals and non-metals leads to environmental pollution. Some more examples are burning of sulphur forms sulphur dioxide and sulphur trioxide, which is a cause for acid rain and soil corrosion. In complete burning of carbon leads to release of poisonous carbon monoxide.

8th Class Physical Science 5th Lesson Metals and Non-Metals InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 68

Question 1.
How will you close the circuit using sulphur, carbon or iodine? They may be in powder form. Try to tightly pack the powder in a straw and use it. Think of other ways!
Answer:
Circuit will not be completed by using non-metals like sulphur, carbon or iodine because they are bad conductors of electricity. So by packing the powder will not complete the circuit. There is no other by using which we can complete the circuit by using a non-metal.

Try This

8th Class Physical Science Textbook Page No. 74

Question 1.
Recall the names of the some of the laboratory acids and bases that you know. Write down their names in table and identify metal/non-metal present in them, which form oxides when react with oxygen. Take the help of your teacher.
Answer:

Name of the base	Metal present in it	Name of the acid	Non-metal present in it
Calcium hydroxide (Ca(OH)2)	Calcium (Ca)	Sulphuric acid (H2SO4>	Sulphur (S)
Sodium hydroxide (NaOH)	Sodium (Na)	Hydrochloric acid (HCl)	Chlorine (Cl)
Magnesium hydroxide (Mg(OH)2)	Magnesium (Mg)	Nitric acid (HNO3)	Nitrogen (N)
Zinc hydroxide (Zn(OH2)	Zinc (Zn)	Phosphoric acid (H3PO4)	Phosphorus(P)
Sodium hydroxide (NaOH)	Sodium (Na)	Sulphurus acid (H2SO3)	Sulphur (S)
Cupric hydroxide (Cu(OH)2)	Copper (Cu)	Carbonic acid (H2CO3)	Carbon (C)

Question 2.
Have you seen a periodic table?
Answer:
Yes.

Question 3.
Try to find the metals and non-metals that you come across in the chapter on the periodic table.
Answer:
Metals               Non-metals
1) Zinc               1) Sulphur
2) Copper          2) Chlorine
3) Iron               3) Nitrogen
4) Potassium     4) Carbon
5) Sodium         5) Phosphorus
6) Gold
7) Silver
8) Magnesium
9) Calcium
10) Aluminium

8th Class Physical Science 5th Lesson Metals and Non-Metals Activities

Activity – 1

Question 1.
Observing appearance and colour of some materials:
Observe the appearance of your samples. Look at their colour. Decide whether they appear shining or dull and record your observations in table. If the surface seems dirty, clean it with sand paper.

Sample	Appearance Shining / not shining	Colour
Iron	shining	grey
Zinc	shining	pale green
Copper	shining	red
Sulphur	not shining	yellow
Aluminium	shining	silver white
Carbon	not shining	black
Magnesium	shining	silver white
Iodine	shining	black

a) Which of the samples did not shine even after you cleaned them with sand paper?
Answer:
Sulphur, carbon.

b) Generally metals are lustrous. Do all lustrous materials are metals?
Answer:
No. Some may be non-metals, e.g.: Iodine

c) We all know that mirror is lustrous. Can a mirror be called metal?
Answer:
No. Several properties required to decide if a given material is metal or not.

Activity – 2

Question 2.
Listening the sound produced by some material:

a) Drop a piece of coal on the floor and listen the sound.
Do you think coal is sonorous?
Answer:
No.

b) Take the pieces of zinc, copper, aluminium, magnesium and tightly packed packets of sulphur, carbon and iodine. Drop them one by one, on a hard surface. Listen carefully to the sound produced and record your observation in table.
Answer:

Material sample that	Material sample that
produce sound	do not produce sound
Zinc	Sulphur
Copper	Carbon
Aluminium	Iodine
	Magnesium

c) What similarity do you notice among materials which produce sound?
Answer:
All of them are metals.

d) Which property of metals first attracted the attention of human beings?
Answer:
Metals had the advantage of not just being harder but they could be heated in a fire and moulded or cast into different shapes. This property of metals first attracted the attention of human beings.

e) Do you bring a similar change in the shape of a clay material by beating it?
Answer: Yes, we bring similar change in the shape of a clay material by beating it.

Activity – 3

Question 3.
Identifying malleability of material:
Take a hammer and beat the material samples which are used in Activity-2 and observe the changes in material samples. Record your observations in the table.
Answer:

Observing the change	Name of sample
Flattens	Iron, zinc, copper, aluminium
Breaks/ converts into powder	Magnesium, sulphur, carbon, iodine
No change	—

Some of the samples like zinc, copper are flattened whereas some materials such as carbon, iodine broken into pieces.
The materials which can be flattened into thin sheets are called malleable materials.
Ductility:
We use wires in different situations in our daily life. Look at the samples given in the table.

a) Have you ever seen the wires made up of materials mentioned in the above table?
Answer:
Yes. I have seen the wires made of iron, copper, aluminium.

b) What is the property of drawing material to make wire is called?
Answer:
Ductility.

Activity – 4

Question 4.
Identifying electric conductivity of a material:
Arrange an electric circuit with a battery and bulb. Close the circuit using an iron nail, as shown in figure. Observe whether the bulb glows or not. Record your observations in table. Repeat the same experiment using the other samples and record your observations in the same table.

Sample	Can we convert it into wires
Iron	Yes
Zinc	Yes
Copper	Yes
Sulphur	No
Aluminium	Yes
Carbon	No
Magnesium	No
Iodine	No

a) Do all the samples allow the bulb to glow?
Answer:
No. Materials like iron, zinc, copper allows bulb to glow.

b) What is name given to these material which allows electricity to pass them and make to bulb to glow are called?
Answer:
They are called conductors.

c) Give examples for good conductors of electricity?
Answer:
Copper, iron, aluminium

d) Talk to an electrician. Look at the handles of his tools. Are the handles made of the same materials? If not why?
Answer:
No. The handles of his tools are made of electrical insulating material in order to avoid electrical shock.

Activity – 5

Question 5.
Observing heat conduction by metals:

Take an iron rod. Stick pins on it with the help of wax. Now fix the rod to a stand as shown in figure. Heat one end of the rod with a spirit lamp and see how the pins fall off?

a) Why did the pins fall off from iron rod?
Answer:
Iron rod gains heat from spirit lamp.

b) Pin of which end fell off first?
Answer:
The pin which is near to spirit lamp falls first.

c) What could be the reason for this?
Answer:
The pin falls off because of heat supplied to the iron rod and makes the wax to melt at one end. The wax closer to the flame melted first and the pin falls off. Then the other pins falls. This activity shows that heat moves from one end of the rod to the other. This property of a material is known as conductivity of heat.

d) Go back to the list of samples. On the basis of all the activities carried out, fill the following table.
Answer:

Lab Activity

Conduct an experiment to know the reaction of oxygen with metals and non-metals.
Answer:
Aim: To know reaction of oxygen with metals and non-metals.
Materials required: One metal sample (Magnesium) and one non-metal sample (Sulphur), spirit lamp or Bunsen burner and litmus paper, etc.
Procedure:
Take a small strip of magnesium and burn it. It burns brilliantly and produce white ashes of magnesium oxide due to reaction between magnesium and oxygen. Collect the ashes of magnesium and add some distilled water to it. Test the solution with red and blue litmus papers. Note the changes in table.

Take a small amount of powdered sulphur in a deflagrating spoon and heat it. Sulphur starts burning and forms sulphur dioxide. Introduce the spoon into a jar and cover the jar with a lid to ensure that the gas produced does not escape. Add small quantity of water into the jar quickly replace the lid. Shake the jar well. Check the solution with blue and red litmus papers. Record the changes in table.

Sample	Physical Appearance before reaction	Physical Appearance after reaction	Effect of Litmus Paper
Magnesium	Silver white sheet	White ash	Turns red litmus into blue
Sulphur	Yellow powder	Colourless gas	Turns blue litmus into red

From the table we can observe metallic oxide solutions are basic in nature whereas non metallic oxide solutions are acidic in nature.

Activity – 6

Question 6.
Experiment about reaction of metals with water.
Answer:
Take a 500 ml beaker or a big trough and fill half of it with water. Cut a small piece of sodium (which is kept in kerosene) and put the sodium piece in water using forceps. This piece of sodium floats on the surface of water with a hissing sound.

This shows that sodium is reacting extremely fast with water.
Repeat the same experiment using aluminium, and iron. We will not see any change even after five minutes. This is because these metals react extremely slow with water. This shows metals react with water at different rates.

Activity – 7

Question 7.
Reaction with Acids.
Fill the reactions of the following metals and non-metals with dilute hydrochloric acid and dilute sulphuric acid.
Iron, Zinc, Copper, Sulphur, Aluminium, Graphite, Magnesium and Iodine.

Observation:
We find that some metals react with dilute HCl or H₂SO₄ liberating hydrogen but non-metals usually do not react with acids.

Activity – 8

Question 8.
Reactivity of metals:
Take six beakers and label them a, b, c, d, e and f. Take 50 ml of water in each beaker and dissolve a spatulaful of copper sulphate in beakers ‘a’ and ‘b’. Dissolve a spatulaful of zinc sulphate, in beakers ‘c’ and ‘d’. Iron sulphate in beakers ‘e’ and ‘f’.

• Zinc granules in beaker ‘a and e’
• Iron nail in beaker ‘b and d’
• Copper turnings in beaker ‘c and f’

Leave the beakers undisturbed. Record the changes in the colour of the solution in the table.

Solutions	Observations
Beaker a	The blue colour of copper sulphate disappears and a powdery red mass of copper is deposited at the bottom of the beaker ’a’.
Beaker b	In beaker ’b’ red copper is found at the bottom of the beaker and on the nail leaving light green iron sulphate solution.
Beaker c	No change
Beaker d	No change
Beaker e	No change
Beaker f	No change

a) What could be the reasons behind these changes?
Answer:
In beaker ‘a’, zinc displaces copper from copper sulphate giving rise to colourless zinc sulphate. Iron displaces copper from copper sulphate in beaker ’b’ leaving light green colour of iron sulphate and zinc displaces iron from Iron sulphate by change the colour from light green to colour less:
Copper sulphate + Zinc → Zinc sulphate + Copper
Copper sulphate + Iron → Iron sulphate + Copper
Iron sulphate + Zinc → Zinc sulphate + Iron

b) Do you find any changes in beakers c, d and f?
Answer:
There is no change in beakers c, d and f. The reason is

1. Copper is unable to displace zinc from zinc sulphate in beaker ‘c’.
2. Copper is unable to displace iron from iron sulphate in beaker ‘f’.
3. Iron is unable to displace zinc from zinc sulphate in beaker ‘d’.

c) Why does iron is unable to displace zinc from zinc sulphate?
Answer:
Iron is less reactive than zinc. A more reactive metal can replace a less reactive metal from its salt solution. But a less reactive metal unable to displace a more reactive metal from its salt solution.
The order of reactivity of given metals are Zinc > Iron > Copper

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 3 Matter Around Us Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 3rd Lesson Matter Around Us

8th Class Physical Science 3rd Lesson Matter Around Us Textbook Questions and Answers

Improve Your Learning

Question 1.
Describe an activity which provides the evidence for
a) the motion of particles
b) attraction between particles
c) inter-particle space
Answer:
a) An activity which provides the evidence for the motion of particles:
Materials required: Two 250 ml round bottom flasks, red or blue ink, dropper, Potassium permanganate (KMnO₄) solution.
Procedure:

1. Take two 250 ml round bottomed flasks and fill them with water.
2. Use a dropper and put a few drops of blue or red ink slowly along the sides of first flask.
   
3. Use a dropper and put one or two drops of KMnO₄ solution along the sides of second flask.
4. We observe that in the first flask the ink drops slowly diffusing and mix with water, so as to change the colour of water to red/blue.
5. In the second flask we observe that the KMnO₄ solution diffuses fast in the water and the colour of water changes.
6. This activity provides an evidence for the motion of particles.

b) An activity which provides the evidence for the attraction between particles:

1. Open a water tap and allow the water to reach the ground.
2. Now try to break the stream of water with your finger.
3. We can break the stream momentarily, but not permanently.
4. The reason behind the stream of water remaining together is the force of attraction between the water particles.
5. Now try to break a piece of iron nail with your hands.
6. We cannot break it, because the force of attraction between the particles of nail is very high.
7. Do the same with a piece of chalk. We can break it easily, due to the weak attraction forces among the particles of piece of chalk.
8. From the above, we can say that the particles of matter have attractive forces among them to keep the particles together.
9. These forces of attraction are not equally strong in all the forms of matter.

c) An activity which provides the evidence for the inter-particle space:
Materials required: Beaker, water, salt, spoon and a glass rod.
Procedure:

1. Take a graduated beaker and fill it with some water and mark the level of water.
2. Add some salt and stir it thoroughly with a glass rod.
3. Observe the change in water level. There will be no change in it.
   
4. Add some more salt and stir it again.
5. Observe the change in water level. There will be no change.
6. Continue this process till you see some salt remains undissolved in water.
7. From this activity, we can say that solid and liquid particles have some space between them.
8. The solid particles enter into the space between the liquid particles on dissolving solid in liquid.
9. This process continues till all the space in liquid particles is occupied by solid particles.
10. After completion of this occupation, the solid particles, as there is no space to occupy remain undissolved.

Question 2.
Name the characteristics of matter that are demonstrated by diffusion.
Answer:
The characteristics of matter that are demonstrated by diffusion:

1. Matter is made up of tiny particles.
2. Particles of matter have space between them.
3. Particles of solids and liquids diffuse into liquids.
4. Particles of gases diffuse into gases.
5. Rate of diffusion of gases is higher than that of liquids or solids.
6. Particles of solids occupy the space between the particles of liquids on addition of a solid to a liquid.
7. Particles of matter move continuously in liquids and gases.

Question 3.
“When sugar is dissolved in water, there is no increase in volume.” Is it true or false? Comment on the statement keeping in mind the amount of sugar, amount of water, etc.
Answer:
This statement is true.
Reason: When sugar is dissolved in water, the particles of sugar occupy the space between the particles of water. Hence there is no change in the volume of water.
Conditions for observing the change in volume of water:
If we go on adding sugar without increasing the quantity of water, there will be no space between water particles, to be occupied by sugar particles. Hence the sugar remains undissolved.

Question 4.
Is there any change in mass when a substance changes its state? Explain with example.
Answer:

1. Take a beaker and fill it with ice cubes.
2. Find the mass (m₁) of the beaker along with ice cubes using a spring balance.
3. Keep the beaker at rest for some time, till the ice changes into water.
4. Then find the mass (m₂) of the beaker along with water.
5. We observe that m₁ = m₂.
6. We conclude that the mass never changes when a substance changes its state.

Question 5.
Do all substances change from solid to liquid and liquid to gas on heating ? Explain. Ans. All substances cannot change from solid to liquid and liquid to gas on heating.
e.g.:

1. When wood is heated, it cannot change its state from solid to liquid, but the form of substance changes.
2. Mercury/blood.

Question 6.
Define the following terms:
a) Melting point
b) Boiling point
c) Evaporation
Answer:
a) Melting point: The temperature at which a solid melts to become a liquid is called “melting point”.
b) Boiling point: The temperature at which a liquid starts boiling at the atmospheric pressure is known as its “boiling point”.
c) Evaporation : The phenomena of change of a liquid into vapours at any temperature below its boiling point is called “evaporation”.

Question 7.
Correct the following statements.
a) Water boils at 100°C under atmospheric pressure.
Answer:
This is a correct statement.

b) A liquid evaporates above its boiling point.
Answer:
This statement is incorrect.
Reason: Evaporation takes place at any temperature below its boiling point.

c) Solids have the largest inter-particle space.
Answer:
This statement is incorrect.
Correct Statement: The inter-particle space of solids is minimum.
Explanation: The force of attraction between the particles is also very high due to less inter-particle space. Hence solids have definite shape and a fixed volume.

d) Gases have the strongest inter-particle forces.
Answer:
This statement is incorrect.
Correct Statement: Gases have weakest inter-particle forces.
Explanation: The inter-particle space for a gas is maximum. Hence the inter-particle forces are also weak. Due to this gases have no definite shape or fixed volume. They have to be stored in a closed container always.

Question 8.
Why do we prefer to sip hot tea with a saucer rather than a cup ?
Answer:

1. The surface area of saucer is more than the surface area of a cup.
2. We know that the rate of evaporation increases with an increase of surface area.
3. The hot tea particles can easily escape from the saucer than a cup.
4. Hence hot tea becomes cold easily in a saucer than a cup.
5. So we prefer to sip hot tea with a saucer rather than a cup.

Question 9.
When water solidifies to ice then heat is
a) Liberated
b) Absorbed
c) No change
d) Depending upon the condition heat may absorbed or liberated.
Answer:
a) Liberated

Question 10.
Convert the following temperatures to the Celsius scale.
a) 283 K   b) 570 K
Answer:
a) We know that 273 K = 0°C
283 K = 283 – 273 = 10°C
∴ 283 K = 10°C

b) We know that 273 K = 0°C
570 K = 570 – 273 = 297
∴ 570 K = 297°C

Question 11.
Convert the following temperatures to the Kelvin scale,
a) 27°C   b) 367°C
Answer:
a) 27°C = 27 + 273 = 300 K
b) 367°C = 367 + 273 = 640 K

Question 12.
Fill in the blanks.
a) Matter changes from one state to another either raising the …………… or lowering the ……………..
b) A change in which a solid on heating directly changes into vapour state is called …………….
Answer:
a) temperature, temperature
b) sublimation

Question 13.
Match the following.
a) Conversion of liquid into gas      ( )        (i) gas
b) Non – compressible                    ( )        (ii) solid
c) Maximum expansion                   ( )        (iii) particle
d) Constituents of matter                ( )        (iv) evaporation
Answer:
a) iv
b) ii
c) i
d) iii

Question 14.
How can we smell perfume sitting several meters away from the source?
Answer:

1. We know that the particles of gas are highly mobile in the air.
2. The particles of perfume vapours also move in air for several meters.
3. Hence we can smell perfume, sitting several meters away from the source.

Question 15.
Steam produces more severe burns than boiling water. Think why?
Answer:

1. Steam particles have more energy than the particles of boiling water.
2. This is because particles in water vapour have absorbed additional energy in the form of latent heat of vaporization.
3. So, steam produces more severe burns than boiling water.

Question 16.
Make a model to explain the structure of particles in solids, liquids and gases.
Answer:
Students have to prepare their own models.

Question 17.
How do you appreciate sweating mechanism of human body to control the temperature of the body?
Answer:

1. When we do some physical exercise or hard work, sweating is observed on the body.
2. The sweat evaporates from the surface of our body by absorbing the heat from your body.
3. Thus the particles of liquid absorb energy from our body and escapes to the surroundings.
4. Due to this we feel cool.

Different shaped containers, Beaker, Measuring jar, Conical flask, Round bottomed flask, Test tubes, CNG related Pictures, 50 ml syringe, Incense stick, Scent bottle, Potassium permanganate, Copper sulphate, Long glass tube with scale, Liquid Ammonia, Hydrochloric acid, Cotton, Two rubber corks, Two tongs, Dropper, Water, Salt, Thermometer, Spirit lamp, China dish.

8th Class Physical Science 3rd Lesson Matter Around Us InText Questions and Answers

8th Class Physical Science Textbook Page No. 31

Question 1.
Is there any substance which can be found in three states like water?
Answer:
Yes. The substance which can be found in three states like water is wax.

Question 2.
What are the properties that lead us to consider petrol or milk as liquids?
Answer:
Petrol and milk are considered as liquids because they have no fixed shape. But they get the shape of the container in which they have been poured.

Question 3.
Do solids have definite shape and fixed volume?
Answer:
Yes, solids have definite shape and fixed volume.

8th Class Physical Science Textbook Page No. 32

Question 4.
What is the shape of the water in different containers?
Answer:
Water gets the shape of containers in which it has been poured.

Question 5.
Is it same in all cases or different?
Answer:
Yes, it is same in all cases.

Question 6.
What shape does water take if it spills on the floor?
Answer:
Water spreads on floor if it spills on the floor.

Question 7.
Are the levels of water and milk same?
Answer:
Yes, the levels of water and milk are same.

Question 8.
Can you guess the volume of oil?
Answer:
Volume of the oil is equal to 50 ml.

Question 9.
What does a fluid mean?
Answer:
Fluid is a substance which can flow easily.

8th Class Physical Science Textbook Page No. 33

Question 10.
Does CNG have a fixed volume?
Answer:
No, CNG does not have a fixed volume.

Question 11.
Does CNG have a definite shape?
Answer:
No, CNG doesn’t have a fixed shape. Its shape is depending on the containers.

8th Class Physical Science Textbook Page No. 34

Question 12.
Does the smell from burning incense stick and deodorant spray reach someone on the other end at the same time?
Answer:
The smell from deodorant spray reaches someone on the other end faster than the smell from incense stick.

8th Class Physical Science Textbook Page No. 36

Question 13.
Why do gases diffuse faster than solids and liquids?
Answer:
The molecules in the gas are far from each other i.e., the inter molecular space is very high than in solids and liquids. Hence they have less attractive power. So, gases diffuse faster than solids and liquids.

Question 14.
When does water change into ice and then into vapour?
Answer:
Water when cooled in a refrigerator, it becomes ice. (Decreasing the temperature).

8th Class Physical Science Textbook Page No. 39

Question 15.
What type of changes occur inside the matter during a change of state?
Answer:
Inside the matter, we observe the increase/decrease in volume during the change of state.

Question 16.
How does this change of state take place?
Answer:
Change of state takes place by change in temperature.

Question 17.
What does happen to the particles of matter during a change of state?
Answer:
During a change of state, the kinetic energy of particles may increase/decrease, resulting in the increase/decrease of inter molecular attraction.

8th Class Physical Science Textbook Page No. 41

Question 18.
What will does happe when we apply pressure and compress a gas enclosed in a cylinder?
Answer:
When pressure is applied and compressed the volume of a gas in a cylinder decreases. (According to Boyle’s law).

Question 19.
Will the particles come closer?
Answer:
Yes, the inter molecular space between the particles decreases and they come close.

Question 20.
Do you think that increasing or decreasing the pressure can change the state of matter?
Answer:
Change in pressure can change the state of matter.

Question 21.
Can we liquify gases by applying pressure or reducing temperature?
Answer:
Gases can be liquefied by cooling below its critical temperature. Hence, change in temperature and pressure causes the gases to liquefy.

Question 22.
Do we always need to supply heat or change the pressure for changing the state of matter?
Answer:
It is required. But in some cases like natural evaporation of water, it is not necessary.

Question 23.
Can the change of state from liquid to vapour take place without the liquid reaching its boiling point?
Answer:
Yes, it is possible in case of drying the wet clothes. In the process, water direly changes into vapour form without reaching its boiling point.

Question 24.
Can you give few more examples for evaporation?
Answer:
Evaporation of iodine, drying up of wet body, etc.

Question 25.
What could be the reasons for this type of changes in states?
Answer:
In liquid s, the particles at the surface possess higher energy than particles in the bulk of watt.. The particles on the surface are able to break away from the force of attraction of other particles and change into vapour state.

Think & Discuss

8th Class Physical Science Textbook Page No. 34

Question 1.
Rubber band Activity:
a) Let us stretch a rubber band. Is there a change in its shape?
b) Is rubber band solid or liquid? Why?
Answer:
a) When rubber band is stretched it changes its shape.
b) It is a solid. If stretching is stopped, the rubber band regains its shape. If the stretching is too much, the rubber band permanently loses its shape.
Reason : Rubber band is a solid, but the nature of particles by which the rubber band is made is responsible for the above phenomena.

Question 2.
Powdered salt Activity:
a) Which shape does the powdered salt take?
b) Can you say that salt is a liquid on the basis of change in its shape? Justify your answer. Take a sponge. Observe its shape.
Answer:
a) Powdered salt takes the shape of the container, b) It is a solid.
Justification:

1. Change in shape or state means a complete change in the arrangement of particles.
2. Powdered salt is a composition of tiny particles, which do not change their shape.

Question 3.
Sponge Activity:
Can you compress it? Is it a soild? Why? Think. Is anything coming out from the sponge when it is compressed.
Answer:

1. Sponge can be compressed.
2. It is a solid.

Justification :

1. The inter-particle space is slightly more than a rigid body.
2. So that it can be compressed.

Question 4.
Why can’t you able compress a wooden block ? (or) Why aren’t you able to compress a wooden block ?
Answer:

1. The inter-particle space is very less in a wooden block.
2. So we cannot compress it at ordinary conditions.

8th Class Physical Science Textbook Page No. 42

Question 5.
Why do we wear cotton clothes in summer?
Answer:

1. More sweat is produced from our body during summer due to excess of external temperature.
2. We feel cool when the sweat is evaporated.
3. On wearing cotton clothes, the clothes absorb sweat from our body. So, we feel cool.
4. Other clothes like silk, polyester, etc. cannot absorb sweat.
5. Hence we wear cotton clothes in summer.

Question 6.
Why do we see water droplets on outer surface of a glass containing ice-cold water?
Answer:

1. Ice-cold water in the glass cools its surface.
2. Air around the glass contains water vapour which is warmer than the surface of the glass.
3. Due to the cold glass, air close to its surface will also become cooler.
4. This changes the water vapour in the air around the surface of the glass into water.
5. This water forms small drops on the outer surface of the glass.

Question 7.
Why do pigs toil in the mud during hot summer?
Answer:

1. Generally, the temperature of body is controlled through the sweating evaporation.
2. In the case of pigs, these have less sweat pores on their skin surfaces. So sweating evaporation process does not take place.
3. Because of this type of arrangement in pigs, they toil in the mud ponds more time during hot summer.

8th Class Physical Science 3rd Lesson Matter Around Us Activities

Activity – 1

Identifying the shape and volume of liquids
Question 1.
(a) Prove that the liquids have no fixed shape.
Answer:

1. Collect transparent containers of different shapes.
2. Take some water using the measuring jar.
3. Pour the water in one of the containers.
4. Observe the shape of water.
5. Pour the same water in different containers and observe the shape of water.
6. We observe that the water (liquid) takes the shape of container.
7. We can say that liquids have no fixed shape.
   

(b) Prove that the liquids have fixed volume.
Answer:

1. Take 50 ml of water with a measuring jar.
2. Pour this water in a transparent beaker.
3. Mark the level of water on the beaker and throw the water out.
4. Now measure 50 ml of milk, and pour it in the same beaker.
5. Mark the level of milk on it, and remove milk from the beaker.
6. Now take 50 ml of oil and pour it in the same beaker.
7. Mark the level of oil on it, and remove the oil from the beaker.
8. We observe that the mark on the beaker is same for water, milk and oil.
9. This proves that the liquids have a fixed volume.

Activity – 2

Question 2.
Do the gases have a definite shape and a fixed volume?
Answer:
CNG (Compressed Natural Gas) is stored in a tank. In vehicles CNG is stored in cylinders. We observe that CNG and all other gases neither have a fixed shape nor fixed volume.

Activity – 3

Observing the compressibility of different materials
Question 3.
Prove that the gases are highly compressible than liquids and solids.
Answer:

1. Take a 50 ml syringe.
2. Draw the piston to suck in air.
   
3. Place your finger on the nozzle and press.
4. Observe depth of piston moved into syringe and note the height of air column.
5. We feel hard to press the piston after certain height.
6. Here the air in the syringe is compressed.
7. Now fill water in the syringe and do the same experiment.
8. Note the height of water column when you feel hard to press the piston.
9. Here the height of water column is more than the height of air column.
10. Now take a piece of wood or iron and press it with your thumb.
11. We cannot find any observable change in its volume.
12. From the above observations, we can say that gases are highly compressible than liquids and solids.

Activity – 4

Observing the diffusion of gases
Question 4.
Describe an activity to observe the diffusion of gases.
Answer:

1. Ask your friend to hold an unlit incense stick and stand in one corner of the room.
2. Then you go and stand in the other corner.
3. We cannot observe any smell (This depends on the type of incense stick).
4. Now ask your friend to light the incense stick.
5. After a few seconds, we can observe the smell of incense stick.
6. The scent in the vapour form and smoke mixes with air and moves across the room and reaches our nose.
7. This activity proves that the gases can diffuse.

Activity – 5

Observing the diffusion of liquids
Question 5.
Write an activity which shows the diffusion of liquids.
Answer:
Take 250 ml round bottomed flask with 2/3rd water in it. Use a dropper and put a few drops of blue or red ink or Potassium permanganate (KMnO₄) solution slowly along the sides of the flask.

We can observe that liquids also diffuse into each other like gases.

Activity – 6

Observing the diffusion of particles of solids into liquids
Question 6.
Prove that the particles of solids diffuse into liquids.
Answer:

1. Take a beaker full of water.
2. Add a few crystals of potassium permanganate to it.
3. We observe that the diffusion of potassium permanganate crystal into water and the colour of water changes.
4. Repeat the experiment with crystals of copper sulphate.
5. Here also we observe the diffusion of CuSO₄ crystals into water and the colour of water changes.
6. From the above observations, we found that the particles of solids diffuse into liquids.

Lab Activity Diffusion of two gases
Question 7.
Describe an experiment to measure the speed of diffusion of two gases.
Answer:
Aim: To observe the speed of diffusion of two gases.
Materials required : Long glass tube with scale, liquid ammonia, Hydrochloric acid (HC/), pieces of cotton, two rubber corks and two tongs.

Procedure:

1. Take a one meter long narrow glass tube.
2. Take two pieces of cotton wool.
3. Soak one piece of cotton wool in HCl solution.
4. Soak another piece of cotton wool in NH₃ solution.
5. Insert them separately at the two ends of the tube with the help of tongs.
6. Close the ends of the glass tube with rubber cork and observe.
7. The HCl gives off hydrogen chloride gas and ammonia solution gives off ammonia gas.

Observation:

1. Both gases react together to form a white ring in the tube due to formation of ammonium chloride.
2. Measure the distance of white ring from two ends of the glass tube.

Explanation:
We can observe that the ammonia gas travelled faster. So that the distance of white ring is more from ammonia end than hydrochloric acid end.

Activity – 7

Question 8.
How small are the particles of matter?
Answer:

1. Take a beaker with water. Mark the level of water.
2. Add 1 or 2 crystals of potassium permanganate and dissolve in water.
3. Colour of water changes to light violet.
4. Now take out approximately 10 ml of this solution and add it to 90 ml of clear water in another beaker.
5. Now the colour of water will be lighter than in the previous one.
6. Again take out 10 ml of this solution and add it to another 90 ml of clear water.
7. Carry out this process 4, 5 times and observe the changes in colour of the solution.
8. We observe the water in last beaker also changed to light violet.
9. From this activity we conclude that both solids and liquids are made up of tiny particles.

Activity – 8

There exists space between particles
Question 9.
Write an activity which shows the space between particles.
Answer:

Procedure: Take a graduated beaker and fill it with some water and mark the water level. Add some salt and stir it thoroughly with a glass rod. Observe if there is any change in water level. Add some more salt and stir it again.
Observations: From the activity we can conclude that both solid and liquid particles have some space between them. Hence the solid particles enter into the space between the liquid particles on dissolving solid in liquid. So there is no change in the water level.

Activity – 9

Observing the force of attraction between the particles of matter
Question 10.
Write an activity which provides an evidence for the force of attraction between the particles of the matter.
Answer:
Procedure:
Open a water tap and allow the water to reach the ground. Now try to break the stream of water with our finger. But we cannot break the stream permanently.
We cannot also break a piece of iron nail with our hands. But we can break a piece of chalk with our hands.
Observations: From the above observations we can say that particles of the matter have forces acting between them that keeps the particles together.
It is also clear that this force is not equally strong and different in different forms of matter.

Activity – 10

Effect of temperature on change of state
Question 11.
Write an activity to know the effect of temperature on change of state of matter.
Answer:

1. Take about 100 g of ice in a beaker.
2. Suspend a laboratory thermometer so that its bulb is in contact with the ice.
3. Set up the beaker as shown in the figure.
4. Note the temperature.
5. Now heat the beaker slowly.
   
6. Record the change in temperature after every 30 seconds.
7. Let the ice melt completely.
8. Now place a glass rod in the beaker and continue heating till water starts boiling.
9. After some time all the water will get vapourised.
10. From this we understand that substances around us change state from solid to liquid and from liquid v to gas on application of heat.
11. There are some substances which can change directly from solid state to gaseous state and vice versa without changing into the liquid state.

Activity – 11

Effect of surface area, humidity and wind speed on evaporation
Question 12.
(a) Explain the effect of surface area on the rate of evaporation.
Answer:
Rate of evaporation increases with an increase of surface area.
Explanation:

1. During evaporation process, the particles escape from the surface of liquid.
2. The increase in the surface area provides more scope for particles to escape from the surface.
3. Hence it leads to increase the rate of evaporation.

Ex: Water in a China dish evaporates faster than the water in test tube.

(b) Explain the effect of humidity on the rate of evaporation.
Answer:
Rate of evaporation decreases with the increase in humidity.
Explanation:

1. The amount of water present in air is called humidity.
2. The air around us cannot hold more than a definite amount of water vapour at a given temperature.
3. If the amount of water vapour is high in air, then the rate of evaporation decreases. Ex : Clothes dry slowly on a rainy day than on a normal day.

(c) Explain the effect of wind speed on rate of evaporation.
Answer:
Rate of evaporation increases with the increase in wind speed.
Explanation:

1. Because of increase in wind speed, particles of water vapour move away with the wind.
2. Due to this, amount of water vapour in the surroundings decreases.
3. It leads to increase in the rate of evaporation.
   Ex: Clothes dry faster on a windy day or under fan than a normal day.

AP State Syllabus AP Board 8th Class Social Studies Important Questions Chapter 12 Freedom Movement in Hyderabad State.

AP State Syllabus 8th Class Social Studies Important Questions 12th Lesson Freedom Movement in Hyderabad State

Question 1.
Was there any difference between the attitude of the British and the Nizams when it came to democracy?
Answer:
No. Both suppressed the people.

Question 2.
Write any two demands of Andhra Maha Sabha in 1935.
Answer:
The demands of Andhra Maha Sabha in 1935:

1. Compulsory primary education should be implemented.
2. Mother tongue (Telugu) should be the medium of instruction.

Question 3.
What are the languages spoken in your area?
Answer:
Telugu, Urdu and Hindi are the languages mostly spoken in our area.

Question 4.
What is the medium of teaching in schools and colleges today in our state?
Answer:
The mediums of teaching in schools and colleges today are Telugu and Urdu. There are many schools also which teach in other statutory languages.

Question 5.
Do you think all teaching should be done in one’s mother tongue?
Answer:
No. I don’t think so. The teaching should be in their own mother tongue.

Question 6.
Why do you think it is important to publish books in mother tongues?
Answer:
Books are knowledge giving ones. If they are in other languages, nobody can read them. So to attain knowledge it is important to publish in mother tongues.

Question 7.
Why do you think the doras who were Hindus helped the Razakars?
Answer:
Doras, who were Hindus, ruled as dictators. Razakars also had anti-democratic views and they fought the democratic political parties and communist led peasants. Hence, Doras supported and helped the Razakars.

Question 8.
Why do you think the Nizam rule ended on 26th January 1950?
Answer:
The Constitution of India came into force on that day. So we can say that the Nizam rule ended on 26th January, 1950.

Question 9.
What was the role of women in Telangana Armed struggle?
Answer:
Women in the Telangana Struggle:
Women suffered most under the rule of Nizams and doras. They were constantly harassed. They not only had to work for the landlords but also to serve the visiting officials. Many women were made slaves of the landlords. Such women attended the night schools of Andhra Maha Sabha and decided to join the Sanghams and the Communist Party. Some of them took arms and fought the Razakars, some of them sang songs and inspired people, some of them acted as doctors and nurses. But they had to make supreme sacrifices for the sake of the movement.

Question 10.
What were the demands of the Andhra Maha Sabha in 1935?
Answer:
The demands of Andhra Maha Sabha in 1935:

1. Compulsory primary education should be implemented.
2. Mother tongue (Telugu) should be the medium of instruction.
3. The legitimate rights of the people in Jagirs should be protected.
4. Child marriages should be discouraged.
5. Local Self Government should be introduced.
6. Untouchability should be eradicated and the untouchables should be given due place in the society.

Question 11.
How was the Telangana Armed Struggle in 1947-48?
Answer:
The movement was transformed in 1947-48 into a broad anti-Nizam and anti-feudal struggle demanding merging of Hyderabad with independent India. The people burnt the records of the village officials and moneylenders and seized the grains hoarded by the landlords and the merchants. To broaden the scope of the movement and integrate various sections into it, the demand was raised to merge Telangana with the other Telugu speaking regions to create Vishal Andhra.

Question 12.
How was the Hyderabad state merged in India?
Answer:
When India became independent in 1947, Osman Ali Khan, the Nizam wanted Hyderabad to remain as an independent kingdom. The common people of the state wanted to join Independent India and a large campaign was organized by the Hyderabad State Congress led by Ramananda Theertha. The Razakars attacked them too. Then the Indian government decided to end this anarchy and sent armed forces to Hyderabad. Hyderabad was finally integrated into Indian Union in September 1948.

Question 13.
You read about the demands of Andhra Maha Sabha (1935). Explain in what way the demands are being implemented now.
Answer:

1. Compulsory Primary Education is implemented (RTE Act)
2. Telugu Medium schools are established.
3. All people have legitimate rights irrespective of caste, race, religion and region.
4. Child marriages are banned.
5. Now untouchability is a crime. They are given due place in the society.

Question 14.
Observe the map and fill in the blanks.

1. Hyderabad was in ———–.
2. ———– Green colour (Refer to textbook on P.No. 140) indicates
3. Aurangabad is present in ———–.
4. The Presidency on West side was ———–.
5. The South-west part was ———–.

Answer:

1. Surf-e-Khas
2. Samsthanas
3. Maharashtra
4. Bombay Presidency
5. Jagir.

AP State Syllabus AP Board 8th Class Social Studies Important Questions Chapter 11B National Movement: The Last Phase 1919-1947.

AP State Syllabus 8th Class Social Studies Important Questions 11th Lesson National Movement: The Last Phase 1919-1947

Question 1.
Do you think it is right to give the police such powers to suppress revolts?
Answer:
Terrorism and showing anger through demonstrations are two delicate issues. The police should recognize the tenderness and difference between these two. Then only it is right to give such powers.

Question 2.
“On August 23rd, 1945, Subhash Chandra Bose is reported to have lost his life in an air crash while going from Bangkok to Tokyo,”
Why is the death of Subhash Chandra Bose not confirmed?
Answer:
The death of Subhash Chandra Bose is a puzzle till today. Many people believe that he died on that day. The Indian government appointed 3 commissions on this issue. But it is not yet decided and confirmed.

Question 3.
Who was Subhash Chandra Bose?
Answer:
He was a Swarajist and a radical nationalist.

Question 4.
What is the meaning of ‘Azad Hind‘?
Answer:
Independent Bharath.

Question 5.
When was the Indian flag hoisted in Kohima?
Answer:
It was hoisted in March, 1944.

Question 6.
What are the names of two cities that affected with Atom Bombs in World War II?
Answer:
Hiroshima and Nagasaki are the two cities that affected with Atom Bombs in World War II.

Question 7.
Why do you think people were so much against such laws during the freedom movement?
Answer:

1. Most of the police and higher officials were Britishers at that time.
2. It was most difficult for the people to been the dictatorship.
3. Introducing such laws at that time was like pouring ghee into the fire.

So they were against such laws.

Question 8.
Describe communalism and secularism.
Answer:
Communalism believes in the promotion of the interest of a particular religious community and not the general interests of all. It also believes that the state and government should be run keeping in mind the interest of that particular religious group. This is in contrast to nationalism which believes that the nation is above individual communities and represents the interests of all people including those who may not have any religion at all. This view is also called ‘Secular’ as it holds that the government should neither interfere in the affairs of a religion nor allow any religion to interfere with the government.

Question 9.
Write about Subhash Chandra Bose and INA.
Answer:
Subhash Chandra Bose had been a Swarajist and a radical nationalist. He organized the Indian National Army (INA) with the cooperation of Rash Bihari Bose in Burma and Andamans. The INA consisted of more than sixty thousand soldiers. He received the help of the Japanese in this fight. On 21 st October 1943, the provisional Government of Independent India (Azad Hind) was set up in Singapore. On March 18th, 1944 the INA crossed the frontiers of Burma and entered India with a slogan “Dilli Chalo” – (on to Delhi).
In March 1944, the Indian Flag was hoisted in Kohima. But with the change of fortunes in the war, the launching of a counter-offensive by the British in the winter of 1944-45 and the final defeat of Japan in the Second World War the INA movement collapsed. On August 23rd, 1945, Subhash Chandra Bose is reported to have lost his life in an air crash while going from Bangkok to Tokyo.

Question 10.
The radicals and radical organizations helped the freedom struggle to attain freedom. Explain it.
Answer:
The period after 1940 was characterised by intensive activities of radical organisations like the Communist party, trade unions, women’s organisations, kisan sabhas and dalit organisations. They mobilised the poor and marginalized peasants and workers, tribals and dalits not only against the British but also against the local exploiters like moneylenders, factory owners and upper caste landlords. They were keen that in the new independent India their interests should be properly represented and their long years of suffering should end and they should get equal rights and opportunities. The national movement which was till then dominated by upper class people gained a new dimension and energy which eventually helped to throw out the British rule.

Question 11.
Read the following passages and answer the questions.
Subhash Chandra Bose and INA
Subhash Chandra Bose had been a Swarajist and a radical nationalist. He organized the Indian National Army (INA) with the cooperation of Rash Bihari Bose in Burma and Andamans. The INA consisted of more than sixty thousand soldiers. He received the help of the Japanese in this fight. On 21st October 1943, the provisional Government of Independent India (Azad Hind) was set up in Singapore. On March 18th 1944 the INA crossed the frontiers of Burma and entered India with a slogan “Dilli Chalo” – (on to Delhi).
In March 1944, the Indian Flag was hoisted in Kohima. But with the change of fortunes in the war, the launching of a counter-offensive by the British in the winter of 1944-45 and the final defeat of Japan in the Second World War the INA movement collapsed.
1. Who was Subhash Chandra Bose?
Answer:
He was a Swarajist and a radical nationalist.

2. Whose cooperation was taken to organise INA?
Answer:
The cooperation of Rash Bihari Bose was taken.

3. Who helped Bose in this fight?
Answer:
Japan helped Bose in this fight.

4. What is the meaning of ‘Azad Hind’?
Answer:
Independent Bharath

5. When was the Indian flag hoisted in Kohima?
Answer:
It was hoisted in March, 1944.

Question 12.
Read the following passage and answer the questions.
Germany led by Hitler and his Nazi party wanted to gain control over the whole world and declared war on Britain, France, USSR, and other countries. USA joined on the side of England, France and USSR (called Allied Countries). Germany was supported by Japan and Italy. One of the worst wars in human history broke out in 1939 and lasted till 1945 when USSR’s armies captured Berlin and the USA dropped atom bomb over Hiroshima and Nagasaki in Japan. Most people who cherished the values of democracy and freedom op-posed Hitler and supported the Allied Countries in the war. However, in India it created a dilemma as Indians were at the same time fighting the British.
1. The party of Hitler was
Answer:
Nazi Party.

2. What were the Allied countries?
Answer:
England, France, Russia and USA.

3. Italy supported to
Answer:
Germany.

4. What are the names of two cities that affected with Atom Bombs?
Answer:
Hiroshima and Nagasaki.

5. Was Hitler a democratic personality or a dictator?
Answer:
Hitler was a dictator.

Question 13.
Collect the details of Bhagat Singh and write an essay on it.
Answer:

Bhagat Singh ….
Born on 28-9-1907
Died on 23-3-1931
He was an Indian Nationalist and influential revolutionist.
He is often referred to as Shaheed. He was born in a Sikh family.
He studied European revolutions, movements and attached to anarchist and Marxist ideologies.
Seeking revenge for the death of Lala Lajapathi Roy at the hands of the police, Singh was involved in the assassination of British police officer John Saunders. Together with Bhatukeshwar Dutt, he undertook a successful effort to throw two bombs and leaflets inside the Central Legislative Assembly while shouting slogans of “Inquilab Zindabad”.

Subsequently, they volunteered to surrender and be arrested. Held on this charge he gained widespread national support. When he underwent a 116 day fast in jail, demanding equal rights for British and Indian political prisoners.
During this time, sufficient evidence was brought against him for a conviction in Saunders case.
A trial was orchestrated by a special tribunal and appeal at the Privy Council in England. He was convicted and subsequently hanged for his participation in the assassination of John Saunders.
He is one of the Heroes of our Nation.

Question 14.
The disparities between Hindu and Muslim ¡n our country were raised in 1906? Were they disappeared after independence? Write the reasons for your answers.
Answer:
No, they were not disappeared even after independence, those the present today also. Pak occupied Kashmir, Kargil war, Parliament attack, Mumbai attacks, Hyderabad attacks — Lumbini park, Gokulchat and Dilsukh Nagar reveal this issue.
Reasons:

1. Because of partition of India associated with Pakistan.
2. There was no way that the communal tensions were going to subside.
3. Sensationalism I vote bank over humanism are also other reasons.

Question 15.
Why did World War — II create a dilemma in Indians?
Answer:
The countries in the world joined the two groups in the war.
The people who supported democratic ideas and opposed dictatorship fought against Hitler and supported the allied countries in war. But at the same time India was against the British n our country. So there was a dilemma.

AP State Syllabus AP Board 8th Class Social Studies Important Questions Chapter 20 Understanding Secularism.

AP State Syllabus 8th Class Social Studies Important Questions 20th Lesson Understanding Secularism

Question 1.
In what way is Indian secularism different from that of other democratic countries?
Answer:
The governments of other democratic countries will not interfere in the religions of its people. But the Indian government interferes in the religious matters. Thus it is different from other democratic countries.

Question 2.
Can there be different views within the same religion?
Answer:
Yes. There can be different views within the same religion. Many religions in the world have different views.

Question 3.
Will the government intervene if some religious group says that their religion allows them to practise infanticide? Give reasons for your answer.
Answer:
The government intervenes in this issue.
Reasons:

1. In Indian secularism the state can intervene in religious affairs.
2. This interference will be according to the ideals of the Constitution.

Question 4.
What are the three main schools of thoughts in Buddhism?
Answer:

1. Theravada
2. Mahayana
3. Vajrayana

Question 5.
Read the following passage and answer the questions that follow.
In February 2004, France passed a law banning students from wearing any conspicuous religious or political signs or symbols such as the Islamic headscarf, the Jewish skullcap, or large Christian crosses. This law has encountered a lot of resistance from immigrants who are mainly from the former French colonies of Algeria, Tunisia and Morocco. In the 1960s, France had faced a shortage of workers and, therefore, had provided visas for these immi
grants to come and work in the country. The daughters of these immigrants often wear headscaives while attending school. However, with the passing of this new law, they have been expelled from their schools for wearing headscatves.
1. What was the law?
Answer:
The law was to ban any conspicuous religious or political signs or symbols.

2. Who opposed the law?
Answer:
The immigrants of France opposed this.

3. When was the law passed?
Answer:
In February, 2004.

Question 6.
Read the first two paras and prepare two questions on this.
The most important aspect of secularism is its separation of religion from State power. This is important for a country to function democratically. Almost all the countries of the world will have more than one religious group living in them. Within these religious groups, there will most likely be one group that is in a majority. If this majority religious group has access to State power, then it could quite easily use its power and financial resources to discriminate against and persecute the persons of other religions. This tyranny of the majority could result in the discrimination, coercion and at times, even the killing of religious minorities. The majority could quite easily prevent minorities from practising their religions. Any form of domination based on religion is in violation of the rights that a democratic society guarantees to each and every citizen, irrespective of their religion. Therefore, the tyranny of the majority and the violation of Fundamental Rights that can result from it is one reason why it is important to separate the State and religion in democratic societies.
Another reason that it is important to separate religion from the State in democratic soci-eties is because we also need to protect the freedom of individuals to exit from their religion, embrace another religion or have the freedom to interpret religious teachings differently.
Answer:
1. What is the most important aspect of secularism?
2. Who were in majority in India?

AP State Syllabus AP Board 8th Class Social Studies Important Questions Chapter 19 Social and Religious Reform Movements.

AP State Syllabus 8th Class Social Studies Important Questions 19th Lesson Social and Religious Reform Movements

Question 1.
Compare the efforts of Narayana Guru and Jyotiba Phule. What similarities do you see between them?
Answer:

1. Both opposed caste system.
2. Both established many schools.
3. Both opposed the supremacy of Brahmins.

Question 2.
Recall the teachings of Buddha with regard to the caste system.
Answer:
Buddha preached that ‘All are equal’. He opposed caste and religious discriminations. He treated all his followers equal.

Question 3.
What are the similarities in the approaches of Gandhiji and Ambedkar towards dalits?
Answer:

1. Both worked for dalits.
2. Both were the members of Congress Party.

Question 4.
Do you find any religious idea advocated by the above reformers which was not part of the Bhakti Movement?
Answer:
No. All the reformers advocated the religious ideas of the Bhakti Movement only.

Question 5.
Do you think dalits have equal access to temples, water sources and schools today? What problems do they still face?
Answer:
At present dalits have equal access to temples, water sources and schools. To say frankly they have equal access and reservations also. So we can say that there were no social problems to them.

Question 6.
What did Ambedkar want to achieve through the temple entry movement?
Answer:
Ambedkar wanted to say that ‘All are equal before God and everyone has rights on God”.

Question 7.
Do you think today equal importance is given to the education of girls or do girls still face discrimination?
Answer:
Equal importance is given to girls education with boys. To be frank the girl enrolment is more than boys in some schools and colleges. But in some families girls face discrimination, mostly in some backward states.

Question 8.
What problems do girls face in getting educated which boys do not face?
Answer:

1. Girls are not encouraged for higher education.
2. Girls are not permitted to far off places for education.
3. Some courses are only meant for boys.

Question 9.
To what extent has the treatment of widows changed today?
Answer:
We can say that the attitude of the society is changed. Widows are treated equally with other women. Their elders are only arranging remarriages for them.

Question 10.
Do dalit girls and Muslim girls face special problems in education even today?
Answer:
Nowadays we seldom hear such a news from newspapers that dalit girls are facing some problems from others. They are also receiving education in classrooms along with others. Muslim girls also have separate schools. They are also studying without problems.

Question 11.
Who founded Brahmo Samaj in combined Andhra Pradesh?
Answer:
Veeresalingam founded Brahma Samaj in combined Andhra Pradesh.

Question 12.
On what did Veeresalingam concentrate all his efforts and energies?
Answer:
Veerasalingam concentrated all his efforts and energies on the widow remarriage and abolition of child marriage.

Question 13.
Why was Veeresalingam called ‘Gadya Tikkana’?
Answer:
He was called ‘Gadya Tikkana’ for his writings in prose.

Question 14.
How would the feeling that the dalits were the orginal inhabitants of Telangana and Andhra have helped in boosting the confidence of the dalits?
Answer:
The feeling would raise the confidence in dalits. This confidence would strengthen them in fighting against the discrimination. That led them to their success.

Question 15.
Did all women get the right to vote in independent India?
Answer:
Yes, all women get the right to vote in independent India.

Question 16.
Locate the following in the given India Map.

1. West Bengal
2. Punjab
3. Bombay
4. Aligarh
5. Bhopal
6. Kerala

Answer:

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 7 Coal and Petroleum Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 7th Lesson Coal and Petroleum

8th Class Physical Science 7th Lesson Coal and Petroleum Textbook Questions and Answers

Improve Your Learning

Question 1.
Complete the given analogy.
i) Coal : ExhaustIble :: ———– : InexhaustIble
ii) Coaltar : ———– :: Coke : Manufacture of steel
iii) Petrochemicals : Plastic :: CNG : ———–
iv) Carbondioxide: Global warming :: ———– : Nausea
Answer:
i) Coal : ExhaustIble :: Solar energy : InexhaustIble
ii) Coaltar : Paints :: Coke : Manufacture of steel
iii) Petrochemicals : Plastic :: CNG : Fertilizer
iv) Carbondioxide: Global warming :: Heavy metals : Nausea

Question 2.
Match the following.
Group – A                                                Group – B
i) Natural resource                    ( )          a) Carbonisation
ii) Coal                                       ( )          b) Plastic chair
iii) Petrochemical product         ( )          c) Krishna and Godavari delta
iv) Natural gas                           ( )          d) Plankton
v) Petroleum                              ( )          e) Water
Answer:
i) e
ii) a
iii) b
iv) c
v) d

Question 3.
Multiple Choice Questions:
i) Which one of the following is less polluting fuel?
a) Natural Gas
b) Coal
c) Kerosene
d) Petrol
Answer:
ii) a

ii) The main constituent of coal is
a) Carbon
b) Oxygen
c) Air
d) Water
Answer:
iii) b

iii) Which one of the following material is used for making shoe polish?
a) Paraffin wax
b) Petrol
c) Diesel
d) Lubricating oil
Answer:
i) a

Question 4.
Fill in the blanks.
i) …………… was used in manufacture of steel. (Coke)
ii) The biproduct of coal used in synthetic dyes and paints is ………………. (coal tar)
iii) Coal was formed in areas where large amounts of ………………. was buried under the earth. (forests)
iv) ………………… gas which causes climate change and global warming. (Carbon dioxide)

Question 5.
Name the petroleum products is used for roads surfacing.
Answer:
A petroleum product of bitumen is used for roads surfacing in place of coal tar these days.

Question 6.
Explain the process of formation of petroleum in Earth. (OR)
Explain the process of formation of petroleum in the Earth.
Answer:
Petroleum was formed from the remains of tiny organisms called plankton that were found in the bottom of seas and oceans. Plankton have tiny droplets of oil inside their bodies.
As these organisms died, their bodies settled at the bottom of the sea or ocean and got covered with layers of sand and clay. Over millions of years, due to absence of air, high temperature and high pressure these dead organisms transformed into petroleum.

Question 7.
Project Work:
Compare a CNG run vehicle with that of a diesel run vehicle. What difference do you notice in both cases with respect to pollutants released, level of pollution and cost of fuel? Prepare a report on your findings. You can take the help of a driver to make a report on your observation.
Answer:

Name of the fuel	Cost of the fuel as on today	Pollutants liberated
Diesel/Petrol	Rs. 52.97/ Rs. 72.14 per litre	Carbon monoxide, carbon dioxide, hydro carbons, sulphur dioxide
CNG	Rs. 49 per kg	Carbon dioxide, sulphur dioxide, nitrous oxide

Question 8.
Project Work:
Choose five families of your neighbourhood, collect the information about the measures that they adopt to conserve energy resources in transport and cooking.
Make a report on your observation.
Answer:

The precautionary methods taken by them to conserve energy resources in transport and cooking.
In transport:

1. They do not using their motor vehicles for travelling smaller distances.
2. They are completing small distances by walk or by bicycle.
3. They are regularly servicing their vehicles.
4. They are regularly changing the engine oil of the vehicle.
5. They are travelling at prescribed speed and not applying brakes unnecessarily which increase the milage.

In cooking:

1. They are using cookers.
2. Not preparing to many fries which can increase the fuel consumption.
3. Regularly cleaning the burners of gas stove.
4. Cooking the food with sufficient water.

Question 9.
The following table shows the total power shortage percentage in India from 1991-1997. Show the data in the form of a bar graph taking shortage percentage for the years on the Y-axis and the years on the X-axis.

S.No.	Year	Shortage (%)
1	1991	7.9
2	1992	7.8
3	1993	8.3
4	1994	7.4
5	1995	7.1
6	1996	9.2
7	1997	11.5

a) Is the shortage percentage of power increasing or decreasing?
Answer:
The power shortage not followed a regular trend. It decreased from 1991 to 1992 and then increased in 1993 and then decreased upto 1995 and then increased upto 1997 from the table given.

b) If shortage percentage of power increases year by year, how will it affect on human life? Explain.
Answer:
The effect of shortage percentage of power on human life:
Agriculture: Agriculture mainly depends on electric power for water supply. If there is no sufficient power is available then the yield of food material decreases.
Industry: Industries mainly run with electric power. If electric power is not sufficient then it is major set back for their production.
Economy: Economy drastically affected by shortage of power which will also effects the economic status of people.
Health: Shortage of power also affects the health of people because many cured by operations which required power.
Science and Technology : The growth of science and technology completely get damage due to lack of power because they are mainly depend on power.
So shortage of power drastically affect human life.

Question 10.
Draw a flow chart showing exhaustible and inexhaustible resources and their use.
Answer:

Question 11.
Collect the information about place were we get coal, petroleum and natural gas in Andhra Pradesh and mark the places on outline map of Andhra Pradesh.
Answer:
Coal: Coal is not available in Andhra Pradesh.
Petroleum and Natural Gas: These reserves are spread over in Krishna and Godavari basins of our state.

Question 12.
How do you appreciate the efforts of human beings to discover an alternate energy source like coal and petroleum for their daily use?
Answer:
Earlier people used kiln using wood for cooking food and for travelling they used horses and bullock carts. There was no electricity so their life was miserable. The wood they were using produced lot of pollution. So they required a fuel not only for cooking but also travelling long distances.
In 19th century the use of coal as fuel was the major thing in development of human beings. Steam engine which used coal was invented during industrial revolution. Later electricity was produced from coal. During this period the steam engine was used to power everything from cloth looms to vehicles on land and water.
The petroleum was started as fuel in 1859 then it was used everywhere in the world because it was better fuel than coal and less pollutant. So people were using petroleum products for their needs that is for cooking, transport and machinery, etc. So discovery of using coal and petroleum as fuel changes the life of human beings. So we should have to appreciate human being for their discovery of an alternative energy source like coal and petroleum for their daily use.

Question 13.
Harshith said to his father, “Daddy we can save more fuel by using bicycle instead of bike for going to nearby places”. How do you appreciate Harshith’s comment?
Answer:
I would appreciate Harshith for his comment. We are wasting a lot of fuel for travelling near by places which can be covered either by bicycle or by walk. If we do like this a lot of fuel is consumed. Consuming fuel is producing fuel. So I thoroughly appreciate Harshith for his comment.

Question 14.
Why should people look for alternative sources of fossil fuel? (OR)
Write your opinion on the necessity of discovering an alternate energy sources to coal and petroleum.
Answer:
The entire research and development in the field of sourced energy shows that at present rate of use of the conventional energy sources like fossil fuels will not last for long and also burning fuels release carbon dioxide a green house gas, which causes a climate changes and leads to global warming.
Coal fired power plants emit mercury, selenium, arsenic, lead in addition to green house gases which are harmful to human health and environment and availability of coal decreasing rapidly.
So people should have to look for alternative sources of fossil fuels which are inexhaustible and pollution free.

Question 15.
Assume that you are a driver, what measures do you take to save petrol and diesel?
Answer:

1. I will thoroughly check whether the engine of the vehicle properly working or not otherwise the vehicle consume more fuel and also release poisonous gases.
2. I will thoroughly check the air in the tyres.
3. I did not unnecessarily apply brakes which will consume more fuel.
4. I will replace engine oils for every two or three months.
5. I will run the vehicle in prescribed speed which will increase the milage.
6. I did not allow overload in the vehicle.

Question 16.
“Crude oil and refined fuel when spills into the sea from tanker of ships by accident”. Discuss the consequences of this on environment.
Answer:
Crude oil and refined fuel spills into sea from tanker of ships by accident causes a damage to natural system and kill sea birds, mammals, shell fish and other organisms due to lack of dissolved oxygen in water as oil is less denser than water it floats on water and forming a layer called oil slink and oxygen does not enters into the water.

Question 17.
“The use of CNG and LPG as fuels for automobiles helps us to minimize air pollution and maintains ecological balance.” Do you agree with this statement? If yes explain.
Answer:
Yes, I will agree with the statement. CNG and LPG are completely combustible. CNG is less polluting and it is cleaner fuel releasing small quantity of harmful gases. Similarly LPG is also releases few polluting gases. CNG and LPG does not release hydrocarbons. They only release carbon dioxide and small quantities of sulphur dioxide and nitrous oxide. So using CNG and LPG as fuels for automobiles help us to minimize air pollution and maintains ecological balance.

8th Class Physical Science 7th Lesson Coal and Petroleum InText Questions and Answers

8th Class Physical Science Textbook Page No. 105

Question 1.
How is biodiversity affected by excessive use of fossil fuels?
Answer:
Biodiversity affected by excessive use of fossil fuels:

1. Burning fuels releases carbon dioxide a green house gas, which causes climate changes and leads to global warming.
2. Coal fired power plants emits mercury, selenium, arsenic, lead in addition to green house gases which is harmful to human health and environment.
3. Many paints made from petroleum and heavy metals release toxic products into air. These toxic products cause a variety of health problems including heart, lungs damage, nausea and dizziness.
   So these are harmful effects of excessive use of fossil fuels on biodiversity.

8th Class Physical Science 7th Lesson Coal and Petroleum Activities

Activity – 1

Question 1.
Identifying articles and materials used for various purposes.
Have a look at table. Column A gives the names of some activities and items. Ask your grandparents or other older people about the names of the materials then used for the items given in column A, and write them in column B. Then in column C, write the names of materials being used at present.
Answer:

From activity 1, you have a long list of materials. Some of them like wood, metals (Iron, Silver, Gold etc) were used ten years, fifty years even hundred years ago. Do your grand parents remember using plastic when they were young?
Now think and wirte the answers:
a) How many of these materials were available 10 years ago?
Answer:
Plastic, iron, gold and silver articles were available 10 years ago.

b) How many of these materials were available 50 years ago?
Answer:
The articles made up of wood, iron, silver, gold are available 50 years ago and also articles made up of clay. There is no plastic articles.

c) How many of these materials were available 100 years ago?
Answer:
The articles made up of clay, wood, iron, silver, gold were available 100 years ago.

Activity – 2

Question 2.
List out the natural resources which are limited and which are abundant arid record in table.
Answer:

Resources abundant	Solar energy, wind energy, tidal energy, biomass enery, water
Resources limited	Coal, petroleum, natural gas

a) What will happen if fossil fuel like coal and petroleum are completely exhausted?
Answer:

1. There would be no fuel for cooking.
2. There would be no fuel for transport.
3. There would be no fuel for running machinery.
4. There would be no fuel for producing electricity.
   So life on earth become miserable.

b) What would be our future energy resources?
Answer:
The future energy resources are hydro electric power, solar energy, wind energy, tidal energy, geothermal energy, Ocean Thermal Energy Conversion (OTEC), biomass energy.

c) Are the fossil fuel resources available plenty to meet the future energy needs?
Answer:
No, a survey gives an information that about 2015 the world people would consume half of total reserves of petroleum. Coal also exhaustible resource. We can meet our needs with coal for another 250 – 300 years at the current rate of use.

d) What actions required to meet the future energy needs?
Answer:

1. Do not waste fuel for unnecessary activities.
2. The energy should be properly utilized and the wastage should be minimized.
3. Usage of bicycle in place of motor vehicles for small distances.
4. Using road transport vehicles for travelling larger distances which will minimize fuel consumption.
5. The engine of a vehicle thoroughly serviced in order to minimize fuel consumption.
6. Alternative sources like solar energy, wind energy, tidal energy more utilized.

Activity – 3

Question 3.
Identifying various uses of petroleum.
Look at the figure and find the other uses of petroleum and its products. Fill in the table.

Answer:

Activity – 4

Question 4.
Identifying uses of coal products:

Observe the above picture and list out the uses of coal products in the following table. You can collect more information by the discussion with elders and with your friends.
Answer:

Lab Activity

Conduct an experiment to show that when we heat high quality coal, a gas evolves which can be burnt. (OR)
What are the materials required to demonstrate “burning of coal”? Draw the diagram of the experimental setup. (OR)
How do you prove a high quality coal on heating produces a burning gas?
Answer:
Aim: To show that when we heat high quality of coal a gas evolves which can burn. Material required : Two boiling tubes, rubber corks, iron stands, delivery tube, jet tube, bunsen burner.
Procedure: Take a spoon of powdered coal into a hard boiling tube and fix it to a stand as shown in figure. Close the test tube with a rubber cork and connect it to another.
boiling tube which is partially filled with water and has fixed to other stand, with the help of ‘U’ shaped delivery tube. Arrange a jet tube to the cork of second boiling tube. Heat the boiling tube containing coal strongly with the help of bunsen burner.

We may notice that brownish black vapours evolved in the first boiling tube. These vapours are passed through water in the second boiling tube. Colourless gas bubbles evolve from the water. If we burn the gas that is evolving through the jet tube we can witness a bright flame at the nozzle. This shows when we heat high quality coal a gas evolves which can burn.

Activity – 5

Question 5.
Group discussion on misuse of fuel resources and its consequences.
Discuss in small groups how fuel resources are being misused in our daily life while doing various activities like
a) transportation, b) cooking and c) industrial use.
Answer:
Misuse of fuel in transportation:

1. Do not stopping the engine at traffic signals.
2. Running the vehicle with more speed than prescribed speed.
3. Unnecessarily using brakes.
4. Not servicing the engine regularly.
5. Not changing the engine oil regularly.
6. Not filling air in the tyres regularly.
7. Carrying overload in the vehicle.
8. Using vehicles for smaller distances.

Misuse of fuel in cooking:

1. Not stopping the burners when the cooking is over.
2. Using more water than required which will consume more fuel.
3. Not checking the burners regularly whether they are any dust particles which will lead more consumption of fuel.
4. Preparing more fries which required more fuel.

Misuse of fuel in industries:

1. Machinery is not properly working.
2. Any flaws in the machinery.
3. Not doing regularly maintenance of machinery.
4. Lubricants are not used properly.

a) What are the consequences of misuse of fuels?
Answer:

1. Fossil fuels like coal and petroleum are completely exhausted.
2. Misuse also leads to environmental pollution due to release of harmful gases like carbon monoxide.

b) What methods could you suggest to prevent the misuse of fuels?
Answer:
In transportation:

1. Drive at a constant and moderate speed as far as possible.
2. Switch off the engine at traffic lights or at a place where you have to wait.
3. Ensure correct tyre pressure.
4. Ensure regular maintenance of the vehicle.

In cooking:

1. Stop the burners when the cooking is over.
2. Use sufficient water for cooking.
3. Do not prepare more frying food.
4. Ensure regular maintenance of the gas stove.

In industry:

1. Correct the flaws in the machinery.
2. Ensure regular maintenance of machinery.
3. Lubricants are used whenever necessary.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 1 Force Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 1st Lesson Force

8th Class Physical Science 1st Lesson Force Textbook Questions and Answers

Improve Your Learning

Question 1.
What is a force? What changes can be produced by a force?
Answer:
Force: A push or a pull of an object is called a force.
Changes produced by a force:

1. A force can change the state of motion of an object.
2. A force can change the shape of an object.

Question 2.
State an example for a situation mentioned below in which a force:
a) Changes the speed of an object.
b) Changes the shape of an object.
c) Changes the direction of an object.
Answer:
a) Force changes the speed of an object:
A ball at rest begins to move when a force is applied on it that shows force changes the speed of an object.
b) Force changes the shape of an object:
Take a plastic or metal scale placed between two bricks and put some weight at the centre of the scale. We observe that force changes its shape.
c) Force changes the direction of an object:
Kick a moving football with some angle then we can observe the change in the direction of football.

Question 3.
How can you differentiate between a contact force and a force at a distance?
(OR)
Distinguish between a contact force and a force at a distance.
Answer:

Contact force	A force at a distance
1. Force which results when there is a direct physical contact between two interacting objects is known as contact force.	1. The force which occurs without any physical contact between two objects is known as a force at a distance or field force.
2. The two objects have direct contact.	2. No contact.
3. For example, the tyres of a bicycle has direct contact with the surface of the road.	3. For example, the attraction of two magnets.

Question 4.
Give two examples each for a contact force and a force at a distance.
Answer:
Contact force:
e.g.: 1) Muscular force 2) Frictional force Force at a distance:
e.g.: 1) Magnetic force 2) Electrostatic force

Question 5.
Detect the errors in the following statement and rewrite it making necessary corrections.
“Because the car is at rest, no forces are acting on it.”
Answer:
The object is said to be at rest when no forces are acting on it or net force acting on it is zero. So the statement should be corrected like this “Because the car is at rest, no forces are acting on it or net force on the car is zero.”

Question 6.
Why do tools meant for cutting always have sharp edges?
Answer:
The tools meant for cutting have sharp edges because of smaller contact area they exerts more pressure on objects and cutting of objects are easy.

Question 7.
Objects change their state of motion due to the net force acting on them. Do you agree with this statement ? Discuss with examples.
Answer:
Yes, we can agree with this statement. Net force can increase or decrease the speed of an object. Force can also change the direction of an object.
Hence we conclude that net force can change the state of motion of an object.
Some examples:

1. If we kick the ball it will move from state of rest.
2. If we stop the running ball it will come to state of rest.
3. If we through a ball on the ground it will come to rest after sometime due to gravitational force acting on it.
4. If we pull the chair, it will move due to muscular force acting on it.

Question 8.
When you push a heavy object, it doesn’t move. Explain the reason in terms of net force.
Answer:

When we apply force on a heavy object it has to overcome frictional force in order to move. If the force applied is less than the frictional force then the net force (f – F) is insufficient to move the object.

Question 9.
Find net forces from the following diagrams:

Answer:
a) Net force is 6N along horizontal direction towards right.
b) Net force is zero.
c) Net force is 14N along horizontal direction towards right.
d) Net force is 1 N upwards in vertical direction.

Question 10.
Imagine that friction has disappeared from the earth. What will happen? Explain.
Answer:
If friction has disappeared from the earth then

1. we cannot walk or run.
2. we will not have any cars or bicycles because all of them move due to friction.
3. no building could be constructed.
4. carpenters will not able to smoothen surfaces.
5. we could not fix nail on the wall.
6. it will not possible to write with pen or pencil.
7. we will not able to hold any appliances such as hammer, soap, etc.

Question 11.
Karthik is observing the live telecast of a one day cricket match. He noticed motion of a roller on the pitch during lunch break. He thought about various forces acting on the roller and the net force when it is in motion. Many questions arose in his mind regarding the direction of the net force. Can you guess what would be those questions?
Answer:

1. Why there is no motion for roller in vertical direction?
2. What are the forces acting in the vertical direction?
3. What are the forces acting in the horizontal direction?
4. Why there is motion in the horizontal direction for roller?

Question 12.
a) Take two identical straws and suspend one of them freely. Rub the other straw with a piece of paper. Bring the rubbed end of the straw near the suspended one. What do you observe from this activity? Can you tell which type of force is it?
b) Comb your dry hair. Bring the comb near small pieces of paper. What do you observe? Explain.
Answer:
a) The rubbed end of the straw attracts the suspend straw when it is brought near to it. The reason is that when the straw is rubbed with a paper, it acquires an electrostatic charge on its surface and the suspended straw near it acquires opposite charge.
b) When we comb dry hair and bring small pieces of paper they are attracted by comb the reason is when we comb dry hair, it acquires electrostatic charge and paper pieces brought near to it acquire opposite charge there by they are attracted by comb.

Question 13.
Collect pictures from various sources like internet, magazines, newspapers, etc. to illustrate contact forces, forces and prepare a scrap book.
Answer:

Question 14.
A stick is placed on steps as shown in the figure. Draw normal forces on the stick.

Answer:

Question 15.
A monkey hangs stationary at the end of the vertical vine. What forces act on the monkey
Answer:
a) The weight of the monkey downward direction.
b) The normal force by branch upward direction.
c) The frictional force exerted by branch along the horizontal direction.

Question 16.
If you push on a heavy box which is at rest, you must exert some force to start its motion. However, once the box is sliding, you can apply a lesser force to maintain that motion. Why?
Answer:
When the box is sliding, the contact points on its surface do not get enough time to lock in to the contact points on the floor. So friction is less when compared with box at rest so we required to apply lesser force to maintain motion.

Question 17.
How do you increase the pressure by keeping
(a) area unchanged and (b) force unchanged?
Answer:
Pressure P = hdg. So pressure can be depend on height of air column, density of air and acceleration due to gravity.
So pressure can be increased by increasing length of air column at a particular place and for a particular gas.

Question 18.
Design and conduct experiments to test few ways how friction may be reduced.
Answer:
Friction is due to the roughness of surfaces. It can be reduced by the following methods.
– By polishing the rough surface.
– By applying lubricants like oil and grease to the surfaces.
– By spreading powder on the rough surface like carromboard.
– By using soap and detergent solutions, etc.
Experiment: The rusted pulley makes a rattling noise. Apply some oil in between the wheel and axle. The sound is reduced and now it works smoothly.

Question 19.
Observe the figure and find in which direction the force of friction acts. Also indicate the normal forces and their directions.

Answer:

f: force of friction
N₁, N₂, N₃, N₄ are normal forces.

Question 20.
A man is standing still on a level floor. What forces act on him? Draw a free body diagram (FBD) to show all forces acting on him.
Answer:
The forces acting on the man:

Along vertical direction:

1. Weight of the man or gravitational force acting vertically downwards.
2. Normal force or reaction applied by the floor vertically up.

Along horizontal direction:
Frictional force applied by the floor on the man.

Question 21.
How do you appreciate the role of friction in facilitating our various activities?
Answer:
Every motion that occurs on earth depends upon friction. For example, we are unable to walk if there is no friction and we cannot write with a pen and we cannot construct a building and there should be no vehicles without friction.
So without friction there is no motion on earth. So friction is required for better living of human beings.

8th Class Physical Science 1st Lesson Force InText Questions and Answers

8th Class Physical Science Textbook Page No. 3

Question 1.
When an object slips off your hand, it always falls down. What pulls it down?
Answer:
Gravitational force.

Question 2.
If you roll a ball on a level ground, it slows down and after sometime it will come to a stop. What makes the ball stop?
Answer:
Frictional force acting between floor and ball.

Question 3.
What forces acting on objects, change their state or state of motion?
Answer:
Contact force and force at a distance.

Question 4.
Why does the needle of a magnetic compass move when we place a bar magnet near to it?
Answer:
A force at a distance or field force acts on the needle. So, the needle of a magnetic compass moves when we place a bar magnet near it.

Question 5.
Why does the toothpaste come out when we press the tube?
Answer:
A contact force acts between our hand and tube. So, the toothpaste comes out when we press it.

Question 6.
Have you observe the difference between the force applied by a magnet on the needle of a compass and the force you applied on the tube?
Answer:
First one is force at a distance and the second one is contact force.

8th Class Physical Science Textbook Page No. 4

Question 7.
If a pen slips off from our hands it falls down to the floor.
a) Why does the pen fall down ?
b) What is the force which pulls the pen down ?
Answer:
a) Due to increase of gravitational pull of the earth than the normal force,
b) Gravitational pull of the earth.

Question 8.
If we keep the pen on a table, it does not fall down. Why ?
Answer:
As the normal force and gravitational pull of the earth are equal, it does not fall down.

Question 9.
a) Why does a stone thrown up into the sky fall back to the earth?
b) Why do rivers flow down to the sea?
c) How does the earth hold the atmosphere?
d) Is there any force pulling the objects towards earth?
Answer:
For all the above questions, the answer is ‘due to gravitational pull of the earth on the nearer bodies of the earth’.

8th Class Physical Science Textbook Page No. 6

Question 10.
In all the actions that we perform in our daily life like brushing, bathing, eating, writing, driving and walking ; we have to exert a force. Do you know from where the force comes?
Answer:
The force comes from our muscles.

8th Class Physical Science Textbook Page No. 8

Question 11.
Did you ever experience slipping on a floor? What conditions caused you to slip?
Answer:
Yes, it was due to less friction between my foot and floor.

Question 12.
Did you experience slipping while you are walking on wet mud ? Why do most of road accidents happen during rainy days?
Answer:
Yes, in the wet mud the friction is very less and wet mud acts as a lubricant between our feet and floor. During rainy season the mud or road will be wet and as mentioned above the friction will be less, so most accidents happen.

Question 13.
Would it be possible to drive a car if there were no friction between the tyres and the road?
Answer:
No, we can’t stop the car as there is no friction in case of no friction between the tyres of car and the road. We can drive, but the car would not get any control.

Question 14.
Place your science book on the table. Is it in a state of rest?
Answer:
Yes.

8th Class Physical Science Textbook Page No. 9

Question 15.
What is the state of the stone?
Answer:
At rest.

Question 16.
What forces are acting on it?
Answer:
Tension and gravitational pull of the earth.

Question 17.
What will happen if the thread is broken?
Answer:
The gravitational pull of the earth increases and the stone falls down.

Question 18.
What do we call this force ? (the force supporting the stone)
Answer:
Tension.

8th Class Physical Science Textbook Page No. 13

Question 19.
You might have seen children playing with a rubber tyre by pushing it with a stick.
They push the tyre again and again with the stick to increase its speed,
a) Do you understand why the speed of the tyre increases whenever it is pushed by the stick?
Answer:
With every push they are applying a little more force on the moving tyre in the direction of motion. Hence the speed of the tyre increases continuously.
b) Give some more examples where the object speeds up or slows down or a change may occur in its direction of motion, when we exert a force on it?
Answer:
If wind blows in the direction of motion of bicycle the speed of bicycle increases. If wind blows in the opposite direction of motion of bicycle the speed of bicycle decreases.

Think and Discuss

8th Class Physical Science Textbook Page No. 5

Question 1.
A cricket ball of mass’m’ is thrown upward with some initial speed. If the air resistance is neglected, what forces are acting on the ball when it reaches (a) half its maximum height and (b) its maximum height?
Answer:
The forces which are acting on the ball thrown vertically upward:
a) At half of its maximum height:

1. The remaining force which acts vertically upwards (some force that we applied is utilized in reaching half of maximum height).
2. The gravitational force downwards.

b) At maximum height:
Gravitational force acts downward direction (The applied force is completely utilized in reaching maximum height).

8th Class Physical Science Textbook Page No. 6

Question 2.
Two identical bars, one which is steel and the other a magnet, are painted with the same colour. How can you tell which one is the magnet using only these two bars? (don’t break the bars)
Answer:
The bar which attracts the other bar is magnet. The other bar is magnetic material that is steel.

8th Class Physical Science Textbook Page No. 8

Question 3.
A book placed on a table is at rest. Is the force of friction acting on it or not ? Explain.
Answer:
Friction is caused by the irregularities on the two surfaces in contact. Even those surfaces which appear very smooth have large number of minute irregularities on them. Irregularities on the two surfaces lock into one another. So a book placed on a table is at rest experiences frictional force.

8th Class Physical Science Textbook Page No. 10

Question 4.
A system of two bodies A and B are placed as shown in figure. How many forces are acting on A and B respectively?
Answer:

On A

1. Normal force exerts by floor vertically upwards.
2. Weight of A vertically downwards.
3. Frictional force exerts floor along horizontal direction.

On B

1. Normal force exerted by surface of A vertically upwards.
2. Weight of B vertically downwards.
3. Frictional force exerts by surface of A along horizontal direction.

Question 5.
Why is it necessary to separate contact force into a normal force and frictional force? Give at least two reasons.
Answer:
Reasons:

1. In order to know what are the forces acting on the object.
2. To know the net force acting on the body.
3. To know the direction of motion of an object.

8th Class Physical Science Textbook Page No. 12

Question 6.
Play arm wrestling with your Mend. How can you explain the winning of the game by using the concept of net force?
Answer:
The person we exerts more muscular force tends to win.

Question 7.
Name the forces acting on arm and their direction while playing the game. Try to draw FBD for this situation.
Answer:
The muscular force, normal force and weight (gravitational force).

8th Class Physical Science Textbook Page No. 15

Question 8.
Does pressure have direction? Explain.
Answer:
Pressure exerts in all directions. So there is no specified direction for pressure. So we does not consider pressure has direction i.e., it has only magnitude but not direction. So it is a scalar quantity.

8th Class Physical Science 1st Lesson Force Activities

Activity – 1

Question 1.
Identifying push or puli:
Write push or pull in the blank boxes given below. If you feel that the action involves both push and pull, write both in the boxes.
Answer:

a) List three more activities where we exert force which appears as a push.
Answer:

1. Pushing a repaired car.
2. A football player taking a penalty kick.
3. A cricket ball hit by a batsman.

b) List three more activities where we exert a force as a pull.
Answer:

1. Drawing bucket of water from a well.
2. Opening a drawer.
3. In a game of tug of war, two teams pull the rope in the opposite directions.

c) State three actions which involve both push and pull.
Answer:

1. Moving a book front or back on a table.
2. Opening or shutting a door.
3. Cleaning the floor with a cloth.

d) Shall we call the effort done on an object by means of pushing or pulling as a force exerted on the object?
Answer:
Yes, it is called force.

e) When an object slips off your hand, it always falls down. What pulls it down?
Answer:
Gravitational force.

f) If you roll a ball on a level ground, it slows down and after sometime it will come to a stop. What makes the bail stop?
Answer:
Frictional force acting between floor and ball.

g) What forces acting on objects, change their state or state of motion?
Answer:
Contact force and force at a distance.
Types of forces:

h) Why does the needle of a magnetic compass move when we place a bar magnet near it?
Answer:
Due to magnetic force of magnet.

i) Why does the toothpaste come out when we press the tube?
Answer:
Due to muscular force applied by us on toothpaste.

j) Have you observe the difference between the force applied by a magnet on the needle of a compass and the force you applied on the tube?
Answer:
First one is force at a distance and the second one is contact force.

Activity – 2

Question 2.
Observing the magnetic force :
Take a sewing needle. Rub it with a bar magnet several times always moving the magnet in the same direction.
a) Does the needle get magnetised?
Answer:
Yes. Identify south and north pole of the magnetised needle. Pin a red coloured foam ball to South pole and white ball to North pole of the needle, then drop it in a bowl of water it floats.
Make another needle in the same way. Float both the needles side by side such that like ends facing each other.

b) What happens to the needles? How do they move?
Answer:
They repel each other. They move backwards to each other.

c) Now place the needles in such a way that unlike ends face each other. How do they push or pull each other?
Answer:
They pull each other that means they are attracted.

d) What is this pull or push between two poles called?
Answer:
Magnetic force.

Activity – 3

Question 3.
Observing electrostatic forces :
Take a balloon. Inflate it and tie up the open end. Now cut a paper into small pieces and place them on floor. Rub the balloon with a paper and using the balloon near the pieces of the paper.
a) Are the bits of paper pulled towards the balloon?
Answer:
Yes, the bits of papers pulled towards balloon.

b) Why does the balloon pull or attracts the pieces of paper?
Answer:
When the balloon is rubbed with a paper it acquires charge and it induces opposite charge which brought near to it. So the pieces of paper are attracted by balloon.

c) Try to use pepper and salt in the place of pieces of paper. What do you observe?
Answer:
They do not attracted by the balloon.
Gravitational force: It is our common experience that if a pen slips off from our hands it falls down to the floor.

d) Why does the pen fall down?
Answer:
Some force is acting in downward direction.

e) What is the force which pulls the pen down?
Answer:
Gravitational force exerted by the earth.

f) If we keep the same pen on a table, it does not fall down. Why?
Answer:
The gravitational force exerted by earth is balanced by normal force between pen and surface of the table.

g) Why does a stone thrown up into the sky fall back to the earth?
Answer:
Due to gravitational pull.

h) Why do the rivers flow down to the sea?
Answer:
Due to gravitational force exerted by earth.

i) How does the earth hold the atmosphere?
Answer:
Due to gravitational force exerted by earth.

j) Is there any force pulling the objects towards earth?
Answer:
The force exerted by earth is gravitational force.

k) Where does gravitational force exists?
Answer:
The gravitational force exists everywhere in the universe between the objects having masses.

Activity – 4

Question 4.
Visualizing magnetic field:

Take a bar magnet and place it on a table. Place a thick white paper over it.
On the paper, sprinkle fine powder of iron as shown in the figure. Tab the table or the paper gently with pen/pencil.
a) Do you find the pattern of iron filings there?
Answer:
Yes.

b) Rotate the magnet in different directions and do the same. How has the pattern changed?
Answer:
In different directions that we will observe different patterns.

c) Why the iron filings set pattern around magnet?
Answer:
Iron filings set themselves in a pattern because of magnetic field created by the magnet.

d) What is the space around the magnet called?
Answer:
The space around magnet where its influence can be detected is called magnetic field.

Activity – 5

Question 5.
Preparing a list of examples for muscular force:
List at least ten activities where we apply muscular force to perform various tasks in table.
Answer:

List of activities where we exert force

Lowering a basket

Lifting a bucket from a well

Pushing a car

Pulling a cow

Opening a drawer

Opening or shutting a door

Hitting a cricket ball with a bat

Playing badminton

Digging a bore well

Raising a flag

Activity – 6

Question 6.
Observing the changes in any muscle while working:
Do you feel your muscle get tightened while performing a physical activity? What could be the reason for it?
Answer:
Take a dumbbell and lift it in different ways and observe while doing this exercise which muscle is going to be shortened.
The term muscles refer to multiple bundles of muscle cells held together. Muscles are normally arranged in such a way that, as one group of muscles contract or shortens, another group relaxes or expands. So we feel the muscles get tightened while performing any physical activity.
Force of friction:
When you roll a ball on a level ground it invariably stops after sometime.
a) Why does the ball stop?
Answer:
Due to some opposing force.

b) Is there any hidden force which brings it to stop?
Answer:
Frictional force between floor and ball.

c) If you stop peddling your bicycle on a level road you observe that its speed decreases gradually. Why does the speed of bicycle decrease gradually? Is there any force acting on it which tends to reduce its speed?
Answer:
The speed of bicycle decreases gradually due to some opposing force. The force is frictional force between road and tyre.

Activity – 7

Question 7.
Observing the motion of a ball on different surfaces.
Try to roll a ball on different surfaces like carpet, rough roads, smooth floor, etc. On which surface does the ball roll farther ?
Answer:
On the smooth floor it roll farther the reason is the force of resistance to the motion seems to be more on the rough surfaces than on the smooth surfaces.

Activity – 8

Question 8.
Observing the motion of objects on an inclined plane:
Take a tray. Place a small ice cube, eraser and a rupee coin to stay on a line at one end of the tray. Now slowly lift this end of the tray as shown below.

a) What do you observe?
Answer:
The three objects tends to slide downwards.

b) Which of these three objects slides down first? Why?
Answer:
Ice cube rolls first because the melting of ice takes place
and water acts as lubricant and decrease the frictional force.

c) Do all objects experience the same resistance to motion? If not why?
Answer:
No, all of them does not experience same resistance in motion because the irregularities present in the surfaces of the objects are different.

d) Which of the objects experiences more resistance to motion? Why?
Answer:
The eraser experiences more frictional force due to more normal force exerted on the surface of eraser.

e) Why the change in resistance experienced by the objects though they all slide down on the same plane?
Answer:
The frictional force depends on nature of surface. So different surfaces exerts differed frictional forces, therefore there is a change in resistance.

f) Did you ever experience slipping on a floor?
Answer:
Yes.

g) What conditions caused you to slip?
Answer:
When we walk on a smooth floor.

h) Did you experience slipping while you are walking on wet mud?
Answer:
Yes.

i) Why do most road accidents happen during rainy days?
Answer:
Rain water acts as lubricant which decrease the frictional force between tyre and road thereby vehicles slip more due to that accidents occur more on rainy days.

j) Would it be possible to drive a car if there were no friction between the tyres of car and the road?
Answer:
No, it is not possible.
Normal force:

k) Place your science book on the table. Is it in a state of rest?
Answer:
Yes.

l) Is there any force acting on that book?
Answer:
Yes.

m) Imagine that the table has disappeared suddenly by magic. What will happen then?
Answer:
The book will fall down due to gravitational pull of the earth.

n) When a book is lying on the table, the gravity pulls the book down all the time but it does not fall down. Why?
Answer:
It is supported by the table.

o) What is the force which supports against gravity by pushing it upward called?
Answer:
The force that a solid force exerts on any object in the normal direction is called the normal force.
Tension:
As shown in the figure a stone is suspended with the help of a thread and its free end is tied to the ceiling.

p) What is the state of the stone?
Answer:
The stone is at the state of rest.

q) What are the forces acting on it?
Answer:
Gravitational force acts downwards and the force exerted by string acts upwards.

r) What will happen if the thread is broken?
Answer:
The stone will fall downwards due to gravitational pull.

s) For a stone tied to the thread there exists a force which supports the stone against gavity by pulling upwards. What do we call this force?
Answer:

It is called tension.

t) What is tension?
Answer:
When we stretch a rope or a thread the tightness of rope or thread is called tension. Tension is a contact force.

Lab Activity

Write an activity to measure limiting force beared by a thread:
(OR)
Conduct an experiment to find the limiting force that can be borne by different threads.
Answer:
Aim: To find the limiting force that can be borne by a thread.
Material used: Spring balance, weights, light threads, weight hanger.
Procedure:
i) Arrange the system as shown in figure. Put some small weights like 50 gm on the weight hanger and note the readings of the spring balance. Now, add some more weights to the hanger and note the readings of spring balance. Do the same till the thread is broken.

ii) Separate the whole system from the ceiling, and tie the thread to weight hanger and now slowly pull up the whole system with your hand when there is a small weight on the hanger.
Note down the readings of the balance when the thread is broken that give limiting force beared by a thread.

a) What do you observe from the readings when it pulled up and released to move down?
Answer:
We will observe from the readings that another force is worked on this system when it is pulled up and released move down.

b) Is the thread broken when the whole system is pulled quickly up?
Answer:
No, the thread is not broken when the whole system is pulled quickly up.

Net force:
a) What are the forces acting on an object placed on a floor?
Answer:
Gravitational force (vertically down) and normal force (vertically up).

b) Do you observe any change in the state of rest of that object, because of these forces and why?
Answer:
No, because these forces acting on the object are equal and opposite in direction. Hence there is no change in its state.

c) What is the net force acting on object in this case?
Answer:
Zero.
Imagine that the same object is kept in a lift which is accelerating.

d) How many forces are acting on this object?
Answer:
Weight of the object (vertically down) and accelerating force (vertically up).

e) Is the net force acting on the object zero? Why?
Answer:
No, it is not equal to zero because the object is moving upward with non-uniform motion.

Activity – 9

Question 9.
Effects of net force acting on a table :
a) Try to push a heavy wooden table. Is it hard to push ?
Answer:
Yes.

b) Ask your Mend to help in pushing the table in the same direction, as shown in the figure. Do you find it easier to move the table now? Why?

Answer:
Yes, because both of us applying force in the same direction on the table. So resultant applied force increases so it is easier to move the table.

c) Now ask your Mend to push the table from the opposite side as shown in the figure.

Does it move ? If it moves, then in which direction does it move?
Answer:
If both of us apply same force with equal magnitude the table does not move.
If it moves, it moves in the direction where there is larger force is applied.

d) If we apply two unequal forces F₁, F₂ applied in the same direction and opposite direction (F₁ > F₂) then what is the net force ?

Answer:

If F₁, F₂ act in same direction, net force = F₁ + F₂
If F₁, F₂ act in opposite direction, net force = F₁ + (-F₂) = F₁ – F₂

Activity – 10

Question 10.
Effects of stretched rubber bands on fingers:
Take a rubber band, stretch it using your fingers. When you stretch the rubber band it exerts force on your fingers and you feel the force of pull on your fingers.
a) What happens if you add one more similar rubber band around your fingers and stretch both together to the same length ? Do you feel the combination of two bands exerts a larger force than that of one?
Answer:
Yes, the net force is the combination of two forces. So they exerts larger force.

b) Let us say the force exerted by one rubber band is F units and the force exerted by the second rubber band is also F units. Then what will be the net force of two rubber bands?
Answer:
Net force (F_net) = F + F
= 2F units

c) What is the net force acting on your finger when three, four, etc. rubber bands are used?
Answer:
If three rubber bands are used the net force = F + F + F = 3F
If four rubber bands are used the net force = F + F + F + F = 4F

How to calculate net force from free body diagrams:
Let a car moving with non-uniform speed along a road.
What are the forces acting on the car? What is the net force acting along the vertical direction? What is the net force acting along horizontal direction? Draw all the relevant forces acting on the body by using free body diagram.
Choose a coordinate system with X and Y axis in figure. Sign convention is to be taken along X and Y directions. Add forces algebraically with sign conventions along X and Y axis respectively.
Answer:

The forces acting on the car are, shown in FBD (Free body diagram).
They are Force applied by the engine = F
Friction applied by road = f
Normal forces are N₁ and N₂.
Gravitational force (F_g) = W
∴ Net force along X – direction,
F_{net, x} = f – F
(∵ They act in opposite direction)
Net force along Y – direction,
F_{net, y} = (N₁ + N₂) – W
(∵ They act in opposite direction)

Activity – 11

Question 11.
Effect of force on the direction of motion and state of the body:
Place a football on the ground. The ball will remain in the state of rest unless someone kicks the ball.

a) Kick the ball what happens? Does the ball start moving?
Answer:
Yes, the ball start moving

b) Kick the moving ball again in the same direction.
What will be the result?
Answer:
The speed of the ball increases.

c) Place your hand or leg against the ball. Does the ball stop ?
Answer:
Yes. You might have seen children playing with a rubber tyre by pushing it with a stick. They push the tyre again and again with the stick to increase its speed.

d) Do you understand why the speed of the tyre increases whenever it is pushed by the stick?
Answer:
With every push they are applying a little more force on the moving tyre in the direction of motion. Hence speed of the tyre increases continuously.

e) What happens if net force acts opposite to the motion of an object ?
Answer:
The net force acts opposite to the direction of motion of an object then it either slows down the object or brings it to a stop.

f) Give some more examples where the object speeds up or slows down or a change may occur in its direction of motion, when we exert a force on it?
Answer:
If wind blows in the direction of motion of bicycle, the speed of bicycle increases. If wind blows in the opposite direction of motion of bicycle, the speed of bicycle decreases.

Activity – 12

Question 12.
Effects of net force on direction of moving object:

a) Hit a carrom coin with the striker. Ask your friends to do the same. Does the coin move in the same direction in each case ?
If not why?
Answer:
No, you can observe that when you hit the coin with the striker not only does the coin changes its direction, but the striker changes its direction too.

b) What might be the cause of that?
Answer:
The net force makes a stationary object move and also changes the speed and direction of moving object.

c) Does the force change only the state of motion ? Are there any other effects of force?
Answer:
No, the force changes the direction.

Activity – 13

Question 13.
Effects of force on the shape of an object:
In the given table some situations are given in the first column showing how the force is applied on an object. Observe the shape of the objects carefully before and after applying the force. Mark T for temporary change and ‘P’ for permanent change.
Answer:

Action of force	Change in shape (temporary / permanent)
Stretching rubber band	Temporary
Squeezing sponge	Temporary
Tearing paper	Permanent
Crushing plastic bottle	Permanent
Making chapathi	Permanent
Breaking glass	Permanent

Activity – 14

Question 14.
Change in effect of force with area of contact:
a) Take a pencil. Just push its rounded end on your palm. Now push from the other side of the pencil gently so that the sharp end is on your palm. What difference did you experience? Why?
Answer:
It applies more force when sharp end touches the palm.

b) Why do the porters place turbans (talapaga) on their head when they have to carry heavy loads?
Answer:
The reason is, they are increasing surface area there by they are decreasing the force applied by object.

c) Why do school bags and shopping bags have broad straps as handles?
Answer:
As the surface area increases the force applied by object decreases.

d) Have you ever wondered why the lorries carrying loads have a large number of broader tyres?
Answer:
The effect of force depends on the area of contact on which the force is acting. When the area of contact is more then the force acting is less. So lorries have a large number of broader tyres to carry heavy loads.

Activity – 15

Question 15.
Identifying effects of force:
Take two trays. Fill both the trays with lime powder or fine sand. Now take two rectangular bricks of equal mass and similar shape. Keep one brick vertically in one tray and the other brick horizontally in the second tray.
a) Do both bricks sink to the same depth in lime powder? If not why?
Answer:
No, both does not sink to the same depth. The brick standing vertically sink deeper in lime powder than the brick standing horizontally The reason is the contact area or surface area on which force is acting is smaller and hence pressure exerted by the brick is more.

b) Why does the sharper side of a knife cuts more easily than a blunt side of it?
Answer:
A sharper side of knife has a smaller contact area. Therefore sharper side of knife exerts more pressure than the blunt side.