Gravitation

A body weighs 72 N on the surface of the earth. What is the gravitational force on it, at a height equal to half the radius of the earth?

1. 32 N
2. 30 N
3. 24 N
4. 48 N

The work done to raise a mass m from the surface of the earth to a height h, which is equal to the radius of the earth, is :

1. mgR
2. 2mgR
3. 12mgR
4. 32mgR

A body weighs 200 N on the surface of earth. How much will it weigh half way down to the centre of the earth?

1. 200 N
2. 250 N
3. 100 N
4. 150 N

The kinetic energies of a planet in an elliptical orbit about the Sun, at positions A, B and C are KA, KB and KC, respectively. AC is the major axis and SB is perpendicular to AC at the position of the Sun S as shown in the figure. Then [figure]

1. KA < KB < KC
2. KA > KB > KC
3. KB < KA < KC
4. KB > KA > KC

If the mass of the Sun were ten times smaller and the universal gravitational constant were ten times larger in magnitude, which of the following is not correct?

1. Raindrops will fall faster.
2. Walking on the ground would become more difficult.
3. Time period of a simple pendulum on the Earth would decrease.
4. g on the Earth will not change.

The acceleration due to gravity at a height 1 km above the earth is the same as at a depth d below the surface of earth. Then

1. d = 1 km
2. d = 32 km
3. d = 2 km
4. d = 12 km

Two astronauts are floating in gravitational free space after having lost contact with their spaceship. The two will

1. move towards each other.
2. move away from each other.
3. will become stationary.
4. keep floating at the same distance between them.

At what height from the surface of earth the gravitation potential and the value of g are -5.4 107 J kg-1 and 6.0 m s-2 respectively? Take the radius of earth as 6400 km.

1. 1400 km
2. 2000 km
3. 2600 km
4. 1600 km

The ratio of escape velocity at earth (ve) to the escape velocity at a planet (vp) whose radius and mean density are twice as that of earth is

1. 1 : 4
2. 1 : 2
3. 1 : 2
4. 1 : 2 2

Starting from the centre of the earth having radius R, the variation of g (acceleration due to gravity) is shown by

1. [figure]
2. [figure]
3. [figure]
4. [figure]