Page No 138:
Question 1:
What are the differences between the mass of an object and its weight?
Page No 138:
Question 2:
Why is the weight of an object on the moon 
th its weight on the earth?
Page No 141:
Question 1:
Why is it difficult to hold a school bag having a strap made of a thin and strong string?
Page No 142:
Question 1:
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Page No 142:
Question 2:
You have a bag of cotton and an iron bar, each indicating a mass of 100 kg when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why?
Page No 143:
Question 1:
How does the force of gravitation between two objects change when the distance between them is reduced to half?
Page No 143:
Question 2:
Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?
Page No 143:
Question 3:
What is the magnitude of the gravitational force between the earth and a 1 kg object on its surface? (Mass of the earth is 6 × 1024 kg and radius of the earth is 6.4 × 106 m).
Page No 143:
Question 4:
The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why?
Page No 143:
Question 5:
If the moon attracts the earth, why does the earth not move towards the moon?
Page No 144:
Question 6:
What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled?
Page No 144:
Question 9:
What do we call the gravitational force between the Earth and an object?
Page No 144:
Question 10:
Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why? [Hint: The value of g is greater at the poles than at the equator].
Page No 144:
Question 10:
Amit buys few grams of gold at the poles as per the instruction of one of his friends. He hands over the same when he meets him at the equator. Will the friend agree with the weight of gold bought? If not, why? [Hint: The value of g is greater at the poles than at the equator].
Page No 144:
Question 11:
Why will a sheet of paper fall slower than one that is crumpled into a ball?
Page No 144:
Question 12:
Gravitational force on the surface of the moon is only
as strong as gravitational force on the Earth. What is the weight in newtons of a 10 kg object on the moon and on the Earth?
Page No 144:
Question 15:
A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?
Page No 145:
Question 19:
In what direction does the buoyant force on an object immersed in a liquid act?
Page No 145:
Question 20:
Why does a block of plastic released under water come up to the surface of water?
Page No 145:
Question 21:
The volume of 50 g of a substance is 20 cm3. If the density of water is 1 g cm−3, will the substance float or sink?
Page No 145:
Question 22:
The volume of a 500 g sealed packet is 350 cm3. Will the packet float or sink in water if the density of water is 1 g cm−3? What will be the mass of the water displaced by this packet?
