CBSE Class 11 Gravitation Worksheet B

Gravitation MCQ Questions with Answers Class 11 Physics Chapter 8

Question. The period of revolution of planet A around the sun is 8 times that of B. The distance of A from the sun is how many times greater than that of B from the sun?
(a) 4
(b) 5
(c) 2
(d) 3
Answer. B

Question. The distance of two planets from the sun are 1013 m and 1012 m respectively. The ratio of time periods of the planets is
(a) 10
(b) 10 10
(c) 10
(d) 1/ 10
Answer. B

Question. A planet is moving in an elliptical orbit around the sun. If T, V, E and L stand respectively for its kinetic energy, gravitational potential energy, total energy and magnitude of angular momentum about the centre of force, which of the following is correct ?
(a) T is conserved.
(b) V is always positive.
(c) E is always negative.
(d) L is conserved but direction of vector L changes continuously.
Answer. C

Question. Two astronauts are floating in gravitational free space after having lost contact with their spaceship.The two will
(a) move towards each other
(b) move away from each other
(c) will become stationary
(d) keep floating at the same distance between them. 
Answer. A

Question. Two spheres of masses m and M are situated in air and the gravitational force between them is F. The space around the masses is now filled with a liquid of specific gravity 3. The gravitational force will now be
(a) 3 F
(b) F
(c) F/3
(d) F/9
Answer. B

Question. Gravitational force is required for
(a) stirring of liquid
(b) convection
(c) conduction
(d) radiation
Answer. B

Question. A body of weight 72 N moves from the surface of earth at a height half of the radius of earth, then gravitational force exerted on it will be
(a) 36 N
(b) 32 N
(c) 144 N
(d) 50 N
Answer. B

Question. The earth (mass = 6 × 10²⁴ kg) revolves around the sun with an angular velocity of 2 × 10^–7 rad/s in a circular orbit of radius 1.5 × 10⁸ km. The force exerted by the sun on the earth, in newton, is
(a) 36 × 10²¹
(b) 27 × 10³⁹
(c) zero
(d) 18 × 10²⁵
Answer. A

Question. If the gravitational force between two objects were proportional to 1/R (and not as 1/R²), where R is the distance between them, then a particle in a circular path (under such a force) would have its orbital speed v, proportional to
(a) R
(b) R⁰ (independent of R)
(c) 1/R²
(d) 1/R
Answer. B

Question. 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?
(a) Raindrops will fall faster.
(b) Walking on the ground would become more difficult.
(c) Time period of a simple pendulum on the Earth would decrease.
(d) g on the Earth will not change
Answer. D

Question. Imagine a new planet having the same density as that of earth but it is 3 times bigger than the earth in size. If the acceleration due to gravity on the surface of earth is g and that on the surface of the new planet is g′, then
(a) g′ = g/9
(b) g′ = 27g
(c) g′ = 9g
(d) g′ = 3g
Answer. D

Question. The density of a newly discovered planet is twice that of earth. The acceleration due to gravity at the surface of the planet is equal to that at the surface of the earth. If the radius of the earth is R, the radius of the planet would be
(a) 2R
(b) 4R
(c) 1/4 R
(d) 1/2 R
Answer. D

Question. The acceleration due to gravity on the planet A is 9 times the acceleration due to gravity on planet B.A man jumps to a height of 2 m on the surface of A.What is the height of jump by the same person on the planet B ?
(a) (2/9) m
(b) 18 m
(c) 6 m
(d) (2/3) m
Answer. B

Question. The radius of earth is about 6400 km and that of mars is 3200 km. The mass of the earth is about 10 times mass of mars. An object weighs 200 N on the surface of earth. Its weight on the surface of mars will be
(a) 20 N
(b) 8 N
(c) 80 N
(d) 40 N
Answer. C

Question. 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?
(a) 48 N
(b) 32 N
(c) 30 N
(d) 24 N 
Answer. B

Question. A body weighs 200 N on the surface of the earth.How much will it weigh half way down to the centre of the earth ?
(a) 100 N
(b) 150 N
(c) 200 N
(d) 250 N
Answer. A

Question. 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
(a) 3/2 mgR
(b) mgR
(c) 2mgR
(d) 1/2 mgR 
Answer. D

Question. 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.
(a) 1400 km
(b) 2000 km
(c) 2600 km
(d) 1600 km
 Answer. C

Question. Infinite number of bodies, each of mass 2 kg are situated on x-axis at distances 1 m, 2 m, 4 m, 8 m, ..., respectively, from the origin. The resulting gravitational potential due to this system at the origin will be
(a) − 4/3
G (b) –4G
(c) – G
(d) − 8/3 G
Answer. B

Question. A body of mass ‘m’ is taken from the earth’s surface to the height equal to twice the radius (R) of the earth. The change in potential energy of body will be
(a) 3mgR
(b) 1/3 mgR
(c) mg 2R
(d) 2/3 mgR
Answer. D

Question. A particle of mass M is situated at the centre of a spherical shell of same mass and radius a. The magnitude of the gravitational potential at a point situated at a/2 distance from the centre, will be
(a) GM/a
(b) 2GM/a
(c) 3GM/a
(d) 4GM/a
Answer. C

Question. A body of mass m is placed on earth’s surface which is taken from earth surface to a height of h = 3R, then change in gravitational potential energy is
(a) mgR/4
(b) 2/3 mgR
(c) 3/4 mgR
(d) mgR/2
Answer. C

Question. The ratio of escape velocity at earth (v_e) to the escape velocity at a planet (v_p) whose radius and mean density are twice as that of earth is
(a) 1 : 4
(b) 1: 2
(c) 1 : 2
(d) 1: 2 2
Answer. D

Question. A black hole is an object whose gravitational field is so strong that even light cannot escape from it.To what approximate radius would earth (mass = 5.98 × 10²⁴ kg) have to be compressed to be a black hole?
(a) 10^–9 m
(b) 10^–6 m
(c) 10^–2 m
(d) 100 m 
Answer. C

Question. The radius of a planet is twice the radius of earth. Both have almost equal average mass-densities. VP and VE are escape velocities of the planet and the earth, respectively, then
(a) V_P = 1.5 V_E
(b) V_P = 2 V_E
(c) V_E = 3 VP
(d) V_E = 1.5 V_P
Answer. B

Question. The earth is assumed to be a sphere of radius R. A platform is arranged at a height R from the surface of the earth. The escape velocity of a body from this platform is fv, where v is its escape velocity from the surface of the Earth. The value of f is
(a) 1/2
(b) √2
(c) 1/ √2
(d) 1/3
Answer. C

Question. For a planet having mass equal to mass of the earth but radius is one fourth of radius of the earth. The escape velocity for this planet will be
(a) 11.2 km/s
(b) 22.4 km/s
(c) 5.6 km/s
(d) 44.8 km/s
Answer. B

Question. The escape velocity of a body on the surface of the earth is 11.2 km/s. If the earth’s mass increases to twice its present value and radius of the earth becomes half, the escape velocity becomes
(a) 22.4 km/s
(b) 44.8 km/s
(c) 5.6 km/s
(d) 11.2 km/s
Answer. A

Question. The escape velocity from earth is 11.2 km/s. If a body is to be projected in a direction making an angle 45° to the vertical, then the escape velocity is
(a) 11.2 × 2 km/s
(b) 11.2 km/s
(c) 11.2 / 2 km/s
(d) 11.2 2 km/s
Answer. B

Question. For a satellite escape velocity is 11 km/s. If the satellite is launched at an angle of 60° with the vertical, then escape velocity will be
(a) 11 km/s
(b) 11√3 km/s
(c) 11/√3 km/s
(d) 33 km/s
Answer. A

Question. A remote-sensing satellite of earth revolves in a circular orbit at a height of 0.25 × 10⁶ m above the surface of earth. If earth’s radius is 6.38 × 10⁶ m and g = 9.8 m s^–2, then the orbital speed of the satellite is
(a) 9.13 km s^–1
(b) 6.67 km s^–1
(c) 7.76 km s^–1
(d) 8.56 km s^–1
Answer. C

Question. A satellite S is moving in an elliptical orbit around the earth. The mass of the satellite is very small compared to the mass of the earth. Then,
(a) the linear momentum of S remains constant in magnitude
(b) the acceleration of S is always directed towards the centre of the earth
(c) the angular momentum of S about the centre of the earth changes in direction, but its magnitude remains constant
(d) the total mechanical energy of S varies periodically with time
Answer. B

Question. A geostationary satellite is orbiting the earth at a height of 5R above the surface of the earth, R being the radius of the earth. The time period of another satellite in hours at a height of 2R from the surface of the earth is
(a) 5
(b) 10
(c) 6 √2
(d) 6/√2
Answer. C

Question. If ve is escape velocity and vo is orbital velocity of a satellite for orbit close to the earth’s suface, then these are related by
(a) v_o = √2v_e
(b) v_o = v_e
(c) v_e = √2v_o
(d) v_e = √2v
Answer. D

Question. The radii of circular orbits of two satellites A and B of the earth, are 4R and R, respectively. If the speed of satellite A is 3V, then the speed of satellite B will be
(a) 3V /4
(b) 6V
(c) 12V
(d) 3V /2
Answer. B

Question. A ball is dropped from a spacecraft revolving around the earth at a height of 120 km. What will happen to the ball?
(a) it will fall down to the earth gradually
(b) it will go very far in the space
(c) it will continue to move with the same speed along the original orbit of spacecraft
(d) it will move with the same speed, tangentially to the spacecraft.
Answer. C

Question. A satellite A of mass m is at a distance of r from the centre of the earth. Another satellite B of mass 2m is at a distance of 2r from the earth’s centre. Their time periods are in the ratio of
(a) 1 : 2
(b) 1 : 16
(c) 1 : 32
(d) 1: 2 2
Answer. D

Question. Two satellites of earth, S₁ and S₂ are moving in the same orbit. The mass of S₁ is four times the mass of S₂. Which one of the following statements is true?
(a) The potential energies of earth and satellite in the two cases are equal.
(b) S₁ and S₂ are moving with the same speed.
(c) The kinetic energies of the two satellites are equal.
(d) The time period of S₁ is four times that of S₂.
Answer. B

Question. For a satellite moving in an orbit around the earth, the ratio of kinetic energy to potential energy is
(a) 1/2
(b) 1/ 2
(c) 2
(d) 2
Answer. A

Question. The satellite of mass m is orbiting around the earth in a circular orbit with a velocity v. What will be its total energy ?
(a) (3/4)mv²
(b) (1/2)mv²
(c) mv²
(d) –(1/2)mv²
Answer. D

Question. The mean radius of earth is R, its angular speed on its own axis is w and the acceleration due to gravity at earth’s surface is g. What will be the radius of the orbit of a geostationary satellite ?
(a) (R²g/w²)^1/3
(b) (Rg/w²)^1/3
(c) (R²w²/g)^1/3
(d) (R²g/w)^1/3
Answer. A

More question-

1. The gravitational force between two blocks is F what would happen if a mass of both the blocks as well as distance between them is doubled?

2. A body is weightless at the centre of earth. Why?

3. Where will a body weigh more at Delhi or at Shimla? Why?

4. Find an expression for the weight of a body at the centre of the earth?

5. Find an expression for gravitational intensity due to earth at a point on its free surface.

6. The earths mass is 80 times that of moon and their diameters are in the ratio 4:1 respectively. What is the value of g on moon?

7. Determine the value of g at the bottom of an ocean 7km deep Given that radius of earth is 6370 km and g = 9.8m|s2.

8. Show that value of g at a height h is same as the value of acceleration due of gravity at a depth d = 2h

9. If T be the period of satellite revolving just above the surface of a planet whose average density is p, show that PT² is a universal constant.

10. Define Gravitational potential energy Hence deduces an expression for gravitational potential energy of a body placed at a point sear the surface of earth? 

Click on link below to download CBSE Class 11 Gravitation Worksheet B.