GRAVITATION

Two objects of masses m1 and m2 having the same size are dropped
simultaneously from heights h
1 and h
2 respectively. Find out the ratio of
time they would take in reaching the ground. Will this ratio remain the
same if (i) one of the objects is hollow and the other one is solid and (ii) both
of them are hollow, size remaining the same in each case. Give reason

How does the force of attraction between the two bodies depend upon their
masses and distance between them? A student thought that two bricks
tied together would fall faster than a single one under the action of gravity.
Do you agree with his hypothesis or not? Comment.

How does the weight of an object vary with respect to mass and radius of
the earth. In a hypothetical case, if the diameter of the earth becomes half
of its present value and its mass becomes four times of its present value,
then how would the weight of any object on the surface of the earth be
affected?

The earth is acted upon by gravitation of Sun, even though it does not fall
into the Sun. Why?

Calculate the average density of the earth in terms of g, G and R.

The weight of any person on the moon is about 1/6 times that on the
earth. He can lift a mass of 15 kg on the earth. What will be the maximum
mass, which can be lifted by the same force applied by the person on the
moon?

Identical packets are dropped from two aeroplanes, one above the equator
and the other above the north pole, both at height h. Assuming all conditions
are identical, will those packets take same time to reach the surface of
earth. Justify your answer

Suppose gravity of earth suddenly becomes zero, then in which direction
will the moon begin to move if no other celestial body affects it?

On the earth, a stone is thrown from a height in a direction parallel to the
earth’s surface while another stone is simultaneously dropped from the
same height. Which stone would reach the ground first and why?

What is the source of centripetal force that a planet requires to revolve
around the Sun? On what factors does that force depend?

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 cm3.What will be the mass of the water displaced by this packet?

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?

Why does a block of plastic released under water come up to the surface of water?

In what direction does the buoyant force on an object immersed in a liquid act?

A ball thrown up vertically returns to the thrower after 6 s. Find

(a) the velocity with which it was thrown up,

(b) the maximum height it reaches, and

(c) its position after 4 s.

A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet.

 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?

A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground.

A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate

(i) the maximum height to which it rises.

(ii)the total time it takes to return to the surface of the earth.

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?

Why will a sheet of paper fall slower than one that is crumpled into a ball?

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? 

What do we call the gravitational force between the Earth and an object?

What is the acceleration of free fall?

What is the importance of universal law of gravitation?

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?

If the moon attracts the earth, why does the earth not move towards the moon?

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?

Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?

How does the force of gravitation between two objects change when the distance between them is reduced to half?

 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?

You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?

Why does an object float or sink when placed on the surface of water?

What do you mean by buoyancy?

Why is it difficult to hold a school bag having a strap made of a thin and strong string?

Why is the weight of an object on the moon  thits weight on the earth?

What are the differences between the mass of an object and its weight?

What do you mean by acceleration due to gravity?

What do you mean by free fall?

Write the formula to find the magnitude of the gravitational force between the earth and an object on the surface of the earth.

State the universal law of gravitation