Gravitation

Q 1.

The following figure shows four containers containing a liquid at the same height. Rank them according to the pressure exerted by the liquid on the bottom of the containers in ascending order. a. 1, 2, 3, 4 b. 4. 3, 1, 2 c. 3, 4, 1, 2 d. same pressure in each case.

Q 2.

What is the SI unit of weight ?

Q 3.

Fill in the blanks :
The value of G was found out by _______ by using a ________.

Q 4.

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

Q 5.

Why don’t two objects move towards each other due to gravitational pull between them ?

Q 6.

Define g and G.Establish relation between them.

Q 7.

What do you mean by free fall ?

Q 8.

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

Q 9.

What is the SI unit of mass ?

Q 10.

Can you calculate mass of Earth from Newton’s law of gravitation ?

Q 11.

Fill in the blanks :
The value of g ________ (increases/decreases) as we go upwards from the earth's surface.

Q 12.

Why is G called the Universal Constant?

Q 13.

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

Q 14.

A ball is thrown upwards from the ground of a tower with a speed of 20 m/s. There is a window in the tower at the height of 15m from ground. How many times and when will the ball pass the window? (g = 10 m/s²)

Q 15.

Fill in the blanks :
The SI unit of weight is _______.

Q 16.

Two bodies A and B having masses 2 kg and 4 kg respectively are separated by 2 m.Where should a body of mass 1 kg be placed so that the gravitational force on this body due to bodies A and B is zero ?

Q 17.

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 ?

Q 18.

How are gravitation and gravity related ?

Q 19.

Comment on application of Newton’s third law of motion to gravitation.Illustrate by examples.

Q 20.

Fill in the blanks :
Acceleration due to gravity (g) is _______ (dependent/independent) of mass.

Q 21.

Fill in the blanks :
The value of g ________ (increases/decreases) as we go downwards from the earth's surface.

Q 22.

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 whichthe moon attracts the earth? Why?

Q 23.

Does Law of gravitation obey Newton's third law of motion?

Q 24.

Fill in the blanks :
The acceleration which causes changes only in direction of the velocity of a body is called __________ and it is always directed ___________ the circle.

Q 25.

Fill in the blanks :
A body is said to be in _______ when only gravity acts on it.

Q 26.

Fill in the blanks :
It is the ____________ of the earth, which holds our atmosphere in place.

Q 27.

Fill in the blanks :
Universal gravitational constant G = _____________.

Q 28.

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?

Q 29.

If the distance between two masses is increased by a factor of 4,by what factor would the mass of one of them have to be altered to maintain the same gravitational force ?

Q 30.

If the distance of Earth from the Sun were half the present value,how many days will make one year ?

Q 31.

Mass of an object is 10 kg. What is its weight on Earth ?

Q 32.

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

Q 33.

What is the acceleration of free fall ?

Q 34.

Which force revolves Moon around Earth ?

Q 35.

What is the usual shape of orbits of planets around the Sun ?

Q 36.

Does Newton’s third law of motion apply to gravitational force ?

Q 37.

Then why Is the Earth not seen moving towards the stone ?

Q 38.

Where is ‘g' maximum, on the surface of Earth, above the surface or below the surface of Earth ?

Q 39.

What is the weight of a body of mass 1 kg on Earth ?

Q 40.

In free fall, will heavier objects accelerate more than light ones ?

Q 41.

Write down the equations of motion of objects under the influence of gravitational force of Earth.Explain the meaning of the symbols used.

Q 42.

Explain what is meant by ‘free fall’and acceleration due to gravity.

Q 43.

In Fig.,the line that joins a planet to the sun sweeps out areas $A$₁$A$₂,$A$₃in time intervals 6 weeks,3 weeks and 2 weeks respectively.How are $A$₁ $A$₂,$A$₃ realted ?

Q 44.

A physics teacher explains to his students in class,the subject of motion under gravity.When a body is projected upwards from the ground with a certain velocity a,the velocity goes on decreasing at a constant rate due to gravitational pull of earth.At a certain height,this velocity becomes zero.The body cannot rise further.From this maximum height,the body begins to fall and its velocity goes on increasing at the same constant rate due to gravitational pull of earth.The body would strike the ground with exactly the same velocity (v = u),with which it was thrown initially. This is on the assumption that resistance due to air is zero, either way.
Read the above passage and answer the following questions:
(i) Why is velocity of body on striking the ground the same as initial velocity of projection of the body ?
(ii) Does the body take same time to fail to ground as the time it takes to reach the maximum height ?
(iii) What values of life do you learn from this brief study ?

Q 45.

An object moves in a circular motion due to centripetal force, acting towards the center. The moon also rotates around the earth? Does centripetal force acts on it? Why does the moon not fall on the earth?
OR
Q:If the moon attracts the earth, why does the earth not move towards the moon?

Q 46.

How is gravitational force of attraction between two bodies affected if(i) Mass of both bodies is doubled.(ii) Distance between them is halved.

Q 47.

Does the force of attraction between two objects depend on the properties of intervening medium?

Q 48.

(a) What is the relationship between g and G?
(b) Show mathematically whether g (acceleration due to gravity on the earth) depends on the mass of the object itself or not.
(c) Show that for a given location on the surface of the earth g is almost constant.

Q 49.

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

Q 50.

When a ball is thrown upwards, it falls back to the ground. Name the force which makes it fall.