**Gravitation MCQs and Answers **play important role in various entrance test. Gravitation is one of the most difficult chapter to master in Physics. While solving this topic it becomes more complicated due to lengthy theory. So students often stuck at that point while writing exams like JEE, NEET etc. Students don’t know how to tackle the exam questions on Gravitation. Here you will get all the details regarding Gravity MCQs and answers.

## Gravitation MCQs and Answers

These Gravitation MCQs and Answers covers the following topics:

### Gravitation MCQs and Answers

**1. An object is projected vertically upwards with a velocity (gr) **^{1/2}**. What is the maximum height reached**** by the object if “R” is the radius of the earth and “g” is t****he acceleration due to gravity?**

^{1/2}

a) R/2

b) R

c) 2R

d) 4R

**Answer: **b

**2****. The ratio of the radius of a planet A to that of a planet B is “r”. The ratio of acceleration due to gravity on the planets is “p”. The ratio of escape velocit****ies of the two planets is _____**

a) (pr)^{1/2}

b) (p/r)^{1/2}

c) (pr)

d) (p/r)

**Answer: **a

**3****. What is the minimum velocity required for an object of mass “m” to escape the gravitational**** pull of a planet of mass “M” a****nd radius “R” from its surface?**

a) [(G*M)/R]^{1/2}

b) [(2*G*M)/R] ^{2}

c) [(G*M*m)/R]^{1/2}

d) [(2*G*M)/R]^{1/2}

**Answer: **d

**4****. The escape**** velocity of an object from the surface of the planet does not de****pend on the mass of the object.**

a) True

b) False

**Answer: **a

**5. The escape velocity of the earth is “v”. If an object is thrown vertically upwards with a velocity “kv”, what is the s****peed of the object at infinity?**

a) v/(k^{2}-1)^{1/2}

b) v(k^{2}-1)^{1/2}

c) v^{2}/(k^{2}-1)

d) v^{2} (k^{2}-1)

**Answer: **b

**6. The earth is able to retain ****its atmosphere because of _____**

a) the mean velocities of atmospheric gas molecules which is less than that of the earth’s escape velocity

b) the mean velocities of atmospheric gas molecules which is greater than that of the earth’s escape velocity

c) the gravitational effect of the moon

d) the earth’s magnetic field

**Answer: **a

**7. What does Kepler’s law of period relate?**

a) Time period and semi-minor axis

b) Time period and eccentricity

c) Time period and semi-major axis

d) Time period and area swept by the planet

**Answer: **c

**8. What is the time taken by a planet to sweep an area of 2 million square km if the time taken by the same planet to cover an area of 1 million square km is 36 hours?**

a) 18 hours

b) 36 hours

c) 72 hours

d) 144 hours

**Answer: **c

**9. What is the constant of proportionality in Kepler’s law of periods known as?**

a) Universal gravitational constant

b) Escape velocity

c) There is no constant of proportionality

d) Cannot be determined

**Answer: **c

**10. Kepler’s laws of planetary motion improved ______**

a) the heliocentric theory

b) the geocentric theory

c) the big bang theory

d) the string theory

**Answer: **a

**11. The elliptical orbits of planets were indicated by calculations of the orbit of which astronomical body?**

a) Mercury

b) Earth

c) Earth’s moon

d) Mars

**Answer: **d

**12. If the eccentricities of the planetary orbits were taken as zero, then the sun is at the centre of the orbit.**

a) True

b) False

**Answer: **a

**13. From Kepler’s law of orbit, we can infer that the sun is located _____ of the planet’s orbit.**

a) at the centre

b) at one of the foci

c) at both foci

d) anywhere along the semi-minor axis

**Answer: **b

**14. Kepler’s laws of planetary motion replaced circular orbits with _____**

a) elliptical orbits

b) parabolic orbits

c) conical orbits

d) hyperbolic orbits

**Answer: **a

**15. Kepler’s laws of planetary motion were proposed only for _____**

a) our sun

b) any star in our galaxy

c) any star in the universe

d) stars of other solar systems

**Answer: **a

**16. What is the gravitational force experienced by an object of 10kg 200m away from an object weighing 1 ton?**

a) 1.6675 N

b) 2.6675 N

c) 3.6675 N

d) 4.6675 N

**Answer: **a

**17. Which scientist introduced the universal law of gravitation?**

a) Albert Einstein

b) Isaac Newton

c) Stephen Hawking

d) Nikola Tesla

**Answer: **b

**18. What will be the value of acceleration due to gravity on the surface of the earth if the radius of the earth suddenly decreases to 60% of its present value, keeping the mass of the earth unchanged?**

a) 9.81 m/s^{2}

b) 5.89 m/s^{2}

c) 16.35 m/s^{2}

d) 27.25 m/s^{2}

**Answer**: d

**19. Which scientist introduced the universal law of gravitation?**

a) Albert Einstein

b) Isaac Newton

c) Stephen Hawking

d) Nikola Tesla

**Answer: **b

**20. What will be the value of acceleration due to gravity on the surface of the earth if the radius of the earth suddenly decreases to 60% of its present value, keeping the mass of the earth unchanged?**

a) 9.81 m/s2

b) 5.89 m/s2

c) 16.35 m/s2

d) 27.25 m/s2

**Answer: **d

**21. The value of acceleration due to gravity of earth at the equator is less than that of the poles due to _____**

a) shape and rotation of the earth

b) mass of the sun

c) mass of the earth

d) mass of the moon

**Answer: **a

**22. The weight of an object can be zero but the mass of an object can never be zero.**

a) True

b) False

**Answer: **a

**23. Gravitational force is _____**

a) an imaginary force

b) a long-range force

c) a short-range force

d) the strongest fundamental force

**Answer: **b

**24. What**** are the dimensions of universal gravitational constant?**

a) [M^{2}L^{3}T^{2}]

b) [M^{-1} L^{3} T^{-2}]

c) [M^{-1} L^{3} T^{2}]

d) [M^{1} L^{3} T^{-2}]

**Answer: **b

**25. The value of gravitational constant was first determined by _____**

a) Albert Einstein

b) Isaac Newton

c) Henry Cavendish

d) Stephen Hawking

**Answer: **c

**26. What apparatus did Henry Cavendish use in his experiment to determine the gravitational constant?**

a) 1 bar, 1 small sphere and 1 large sphere

b) 1 bar, 2 small spheres and 2 large spheres

c) 2 bar, 1 small sphere and 2 large spheres

d) 2 bar, 2 small spheres and 1 large sphere

Answer: b

**27. What material were the spheres made up of in Henry Cavendish’s experiment?**

a) Lead

b) Steel

c) Iron

d) Wood

**Answer: **a

**28. What is the value of universal gravitational constant?**

a) 6.022 x 10^{23}

b) 6.67 x 10^{-11} N m^{2}/kg^{2}

c) 1.602 x 10^{-19} C

d) 9.81 m/s^{2}

**Answer: **b

**29. The value of universal gravitational constant changes is which of the following medium****?**

a) Air

b) Water

c) Plasma

d) The gravitational constant is independent of the medium

**Answer: **d

**30. What would be the magnitude of the acceleration due to gravity on the surface of the earth if the radius of the earth were reduced by 20%?**

a) 9.81 m/s^{2}

b) 12.26 m/s^{2}

c) 15.33 m/s^{2}

d) 49.05 m/s^{2}

**Answer:** c

**31. What would be the magnitude of the acceleration due to gravity on the surface of the earth if the density of the earth increased by 3 times and the radius remained the same?**

a) 9.81 m/s^{2}

b) 12.26 m/s^{2}

c) 15.33 m/s^{2}

d) 29.43 m/s^{2}

**Answer:** d

**32. The acceleration due to gravity on the surface of the earth is different at different points on the surface.**

a) True

b) False

**Answer:** a

**33. The acceleration due to gravity on the surface of the earth is _____**

a) greater towards the equator and lesser towards the poles

b) lesser towards the equator and greater towards the poles

c) same at all points on the surface of the earth

d) same everywhere except at the poles

**Answer****:** b

**34. The dimensions of acceleration due to gravity are _____**

a) [M^{0}L^{1}T^{-2}]

b) [M^{1} L^{-1}T^{-2}]

c) [M^{-1} L^{2} T^{-1}]

d) [M^{0}L^{-1}T^{2}]

**Answer: **a

**35. Assume that the earth is a perfect sphere but of non-uniform interior density. Then, acceleration due to gravity on the surface of the earth _____**

a) will be towards the geometric centre

b) will be different at different points on the surface

c) will be equal at all points on the surface and directed towards the geometric centre

d) cannot be zero at any point

**Answer: **d

**36. Which of the following is the variation of acceleration due to gravity at a height “h” above the earth’s surface? Let “R” be the radius of the earth and “M1” the mass of earth.**

a) g = (G*M1)/R2

b) g = (G*M1)/h2

c) g = (G*M1)/(R + h)2

d) g = (G*M1)/(h/R)2

**Answer: **c

**37. Which of the following is the variation of acceleration due to gravity at a height “h” above the earth’s surface? Let “R” be the radius of the earth and “M1” the mass of earth. (Assume h < < R)**

a) g = (G*M1)/R^{2}

b) g = (G*M1)/h^{2}

c) g = (G*M1)/(R/h)^{2}

d) g = [(G*M1)/R^{2}] x [1 – (2h)/R)]

**Answer:** d

**38. Which**** of the following is the variation of acceleration due to gravity at a depth “d” below the earth’s surface? Let “R” be the radius of the earth and “M1” the mass of earth. (Assume the density of the earth to be constant)**

a) g = (G*M1)/(R – d)

b) g = [(G*M1) x density]/d

c) g = (G x M1/R^{3}) / (R – d)

d) g = (G x M1/R^{3}) x (R – d)

**Answer****:** d

**39. What is the relationship between height “h” above the earth’s surface and a depth “d” below the earth’s surface when the magnitude of the acceleration due to gravity is equal? (Assume h < < R; where, R = Radius of the earth)**

a) h = d

b) h = 2d

c) 2h = d

d) 3h = 2d

**Answer: **c

**40. At what height above the surface of the earth, the acceleration due to the gravity of the earth becomes 5% of that of the surface?**

a) h = 0.5 R

b) h = 1.5 R

c) h = 2.5 R

d) h = 3.5 R

**Answer: **d

**41. The time period of a simple pendulum on the surface of the earth is “T”. What will be the time period of the same pendulum at a height of 2 times the radius of the earth?**

a) T

b) 2T

c) 3T

d) 4T

**Answer: **c

**42. The net acceleration due to gravity is zero at all points inside a uniform spherical shell.**

a) True

b) False

**Answer: **a

**43. Let the radius of the earth be R. Now, assume that the earth shrunk by 20% but the mass is the same. What would be the new value of acceleration due to gravity at a distance R from the centre of the earth if the value at the same distance in the previous case was “g’”?**

a) g’

b) 2g’

c) 3g’

d) 4g’

**Answer: **a

**44. ****The acceleration of the moon towards the earth is approximately 0.0027 m/s**^{2}**. The moon revolves around the earth once approximately every 24 hours. What would be the acceleration due to gravity of the earth of the moon towards the earth if it were to revolve once every 12 hours?**

^{2}

a) Become half in magnitude

b) double in magnitude

c) Change direction but remain the same in magnitude

d) Remains unchanged

**Answer: **d

**45. A dam produces electricity from the gravitational potential energy of the water stored in it. The same dam has 50 cubic km of water stored 50 meters above the ground. What is the work done**** by gravity relative to the ground? (Assume g = 10 m/s**^{2}**)**

^{2}

a) 1.5 x 10^{16} J

b) 2.5 x 10^{16} J

c) 3.5 x 10^{16} J

d) 4.5 x 10^{16} J

**Answer: **b

**46. A 4kg eagle picks up a 75g snake and raises it 2.5 m from the ground to a branch. What is the work done by the eagle on the snake? (Assume g = 10 m/s**^{2}**)**

^{2}

a) 100 J

b) 1.875 J

c) 118.75 J

d) 10 J

**Answer:** b

**47. A 4kg eagle picks up a 75g snake and raises it 2.5 m from the ground to a branch. What is the work done to raise the bird’s own centre of mass to the branch? (Assume g = 10 m/s**^{2}**)**

^{2}

a) 100 J

b) 1.875 J

c) 118.75 J

d) 10 J

**Answer: **a

**48. The value of the gravitational potential at the centre of a ring of radius “a” and mass “M” is _____**

a) zero

b) -(G*M)/a

c) -(G*M)/a^{1/2}

d) infinite

**Answer: **b

**49. The gravitational potential energy of a body at a distance “r” from the centre of the earth is V. Its weight at a distance “2r” from the centre of the earth is _____**

a) V/r

b) V/4r

c) V/2r

d) 4V/r

**Answer: **b

**50. The velocity with which an object should be projected from the surface of the earth such that it reaches a maximum height equal to “n” time the radius of earth “R” is _____ (M = Mass of the earth)**

a) [(n*G*M)/(n+1)R] ^{½}

b) [((n+1)*G*M)/(n+1)R] ^{2}

c) [(n*G*M)/(n+1)R]

d) [((n+1)*G*M)/nR] ^{2}

**Answer****:** a

**51. The value of the gravitational field in a region is given by g = 2i + 3j. What is the change in gravitational potential energy of a particle of mass 5kg when it is taken from the origin O(0,0) to a point P(10, -5)? (Letters in bold are vectorial representations)**

a) 5 J

b) 10 J

c) 25 J

d) 50 J

**Answer: **c

**52. The force of gravity is a conservative force.**

a) True

b) False

**Answer: **a

**53. Conventionally, the magnitude of gravitational potential energy for an object at infinity from the earth is _____ ((M = Mass of the earth; m = Mass of the object at infi****nity; R = Radius of the earth).**

a) -(G*M)/R^{2}

b) -(G*M)/R

c) -(G*M*m)/R

d) Zero

**Answer: **d

**54. The maximum value of gravitational potential energy is zero.**

a) True

b) False

**Answer: **a

**55. The escape velocity at the event horizon of a black hole is 3×10**^{8}** m/s, i.e., the velocity of light. What is the mass of the black hole if the distance from its centre to the event horizon is**** 18km?**

^{8}

a) 12.15 x 10^{-30} kg

b) 12.15 x 10^{30} kg

c) Infinity

d) Cannot be determined

**Answer: **b

**56. The radius of the moon is approximately 3.7 times smaller than the radius of the earth. Assuming**** that their densities are same, what is the escape velocity**** of the moon compared to earth?**

a) 0.07 times

b) 0.7 times

c) 7 times

d) 3.7 times

Answer:

**57. A planet as a radius “R” and density “P”. The escape v****elocity of this planet is _____**

a) directly proportional to P

b) inversely proportional to P

c) directly proportional to P^{1/2}

d) inversely proportional to P^{1/2}

**Answer: **c

**58. A particle is kept at a distance R above the earth’s surface. What is the minimum speed with which it should be projec****ted so that it does not return?**

a) [(G*M)/(4*R)]^{1/2}

b) [(G*M)/(2*R)]^{1/2}

c) [(G*M)/R] ^{½}

d) [(2*G*M)/R]^{1/2}

**Answer: **c

**59. The radius of Jupiter is approximately 11 times larger than the earth. Jupiter has a mass 316 times that of earth. What is the approximate escape velocit****y of Jupiter compared to earth?**

a) 100 times greater

b) 12 times greater

c) 5 times greater

d) Equal to that of the earth

**Answer: **c

**60. If the earth lost 99% of its mass, the escape velocity would _____**

a) increase 10 times

b) decrease 10 times

c) decrease 90 times

d) increase 90 times

**Answer:** b

**61. A satellite is launched into a circular orbit of radius R while a second satellite is launched into an orbit of radius 1.02R. What is the percentage change in the time periods of the two sate****llites?**

a) 0.7

b) 1

c) 1.5

d) 3

**Answer: **d

**62. A satellite is revolving very close to a planet of density D. What is the time period of that satellite****?**

a) [3/(D*G)]^{1/2}

b) [3/(D*G)]^{3/2}

c) [3/(2*D*G)]^{1/2}

d) [(3*G)/D]^{1/2}

**Answer: **c

**63. A satellite**** orbits the earth at a height of R/5. What is its o****rbital speed?**

a) [(2*G*M)/(R)]^{1/2}

b) [(G*M)/(R)]^{1/2}

c) [(G*M)/(7*R)]^{1/2}

d) [(5*G*M)/(6*R)]^{1/2}

**Answer: **d

**64. The time period of a satellite is independen****t of the mass of the satellite.**

a) True

b) False

**Answer: **a

**65. The time**** period of a satellite of earth is 90 minutes. If the separation between the earth and the satellite is quadrupled, the new ti****me period will be _____________**

a) 90 minutes

b) 180 minutes

c) 560 minutes

d) 720 minutes

**Answer: **d

**66. The satellites orbiting the earth, eventually fall to the earth when they are left unsupervise****d or unattended because _____**

a) their power supply runs out

b) of viscous forces causing the speed of the satellite and hence height to gradually decrease

c) the laws of gravitation predict such a trajectory

d) of collisions with other satellites

**Answer: **b

**67. Consider 2 satellites A and B having time periods 16 hours and 1 hour, respectively. What is the**** ratio**** of the radius of their orbits?**

a) 4:1

b) 8:1

c) 16:1

d) 64:1

**Answer: **d

**68. The time period of a satellite depends on _____**

a) the mass of the satellite

b) radius of its orbit

c) both mass of satellite and radius of the orbit

d) neither mass of satellite nor radius of the orbit

**Answer: **b

**69. Consider two satellites A and B. Both move around the earth in the same orbit but the mass of B is twice that of the mass of A.**

a) Orbital speeds of A and B are equal

b) The orbital speed of A is twice that of B

c) The orbital speed of B is twice that of A

d) The kinetic energy of both A and B are equal

**Answer: **a

**70. Two satellites of masses 50 kg and 100 kg revolve around the earth in circular orbits of radii 9R and 16R. What is the ratio of speeds of the two satellites?**

a) 3:4

b) 4:3

c) 9:16

d) 16:9

**Answer: **b