Unit 6: Gravitation Class 11 MCQs

Here are some multiple-choice questions and answers related to Unit 6: Gravitation:

1. The force of attraction between two point masses is inversely proportional to the square of the distance between them. This is known as?

A) Kepler’s First Law
B) Newton’s Law of Universal Gravitation
C) Coulomb’s Law
D) Gauss’s Law

Answer: B) Newton’s Law of Universal Gravitation.
Explanation: Newton’s Law of Universal Gravitation states that the force of attraction between two masses is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

2. What is the value of gravitational acceleration (g) at the surface of the Earth?

A) 9.8 m/s²
B) 10 m/s²
C) 6.67 × 10⁻¹¹ N·m²/kg²
D) 0 m/s²

Answer: A) 9.8 m/s².
Explanation: The acceleration due to gravity at the Earth’s surface is approximately 9.8 m/s².

3. The gravitational potential energy of an object near the Earth’s surface depends on?

A) Its mass and velocity
B) Its mass and height above the surface
C) Its velocity and height above the surface
D) Its velocity and mass

Answer: B) Its mass and height above the surface.
Explanation: The gravitational potential energy is given by the formula U=mghU = mghU=mgh, where mmm is the mass, ggg is the acceleration due to gravity, and hhh is the height above the surface.

4. The gravitational force between two bodies depends on?

A) Their masses and the distance between them
B) Only the mass of the larger body
C) Only the distance between the bodies
D) Only the mass of the smaller body

Answer: A) Their masses and the distance between them.
Explanation: The gravitational force is proportional to the product of the masses of the two bodies and inversely proportional to the square of the distance between them.

5. The value of the gravitational constant GGG is?

A) 6.67 × 10⁻¹¹ N·m²/kg²
B) 9.8 m/s²
C) 6.67 × 10⁻¹⁰ N·m²/kg²
D) 9.8 N·m/kg

Answer: A) 6.67 × 10⁻¹¹ N·m²/kg².
Explanation: The gravitational constant, GGG, is 6.67 × 10⁻¹¹ N·m²/kg² and is used in the formula for Newton’s law of universal gravitation.

6. The force of gravity on an object is greater at the Earth’s?

A) Poles than at the equator
B) Equator than at the poles
C) Same at all locations
D) Both poles and equator are equal

Answer: A) Poles than at the equator.
Explanation: The Earth is slightly flattened at the poles, making the distance from the center of the Earth to the poles shorter than the distance to the equator. Therefore, gravity is slightly stronger at the poles than at the equator.

7. Kepler’s Third Law relates the orbital period of a planet to?

A) The distance between the planet and the Sun
B) The mass of the planet
C) The gravitational force on the planet
D) The angular velocity of the planet

Answer: A) The distance between the planet and the Sun.
Explanation: Kepler’s Third Law states that the square of the orbital period of a planet is directly proportional to the cube of its average distance from the Sun.

8. The escape velocity from the Earth’s surface is approximately?

A) 7.9 km/s
B) 11.2 km/s
C) 9.8 m/s
D) 5 km/s

Answer: B) 11.2 km/s.
Explanation: The escape velocity from the Earth’s surface is approximately 11.2 km/s, which is the speed needed to escape Earth’s gravitational pull.

9. A satellite is in orbit around the Earth. Its orbital speed depends on?

A) Only the mass of the satellite
B) Only the mass of the Earth
C) The altitude of the satellite
D) The mass of the satellite and the Earth

Answer: C) The altitude of the satellite.
Explanation: The orbital speed of a satellite depends on the altitude of its orbit, with lower orbits requiring higher speeds.

10. The gravitational force between two masses becomes four times stronger when?

A) The mass of one body is doubled
B) The distance between the bodies is halved
C) Both masses are doubled
D) The distance is doubled

Answer: B) The distance between the bodies is halved.
Explanation: The gravitational force is inversely proportional to the square of the distance between the two masses. Therefore, halving the distance between the masses will increase the gravitational force by a factor of four.

11. Gravitational potential energy is zero when?

A) The object is at the surface of the Earth
B) The object is at infinity
C) The object is at the center of the Earth
D) The object is at the Earth’s poles

Answer: B) The object is at infinity.
Explanation: Gravitational potential energy is defined relative to infinity, where it is zero. As the object moves closer to another mass, the potential energy becomes more negative.

12. If the mass of an object is doubled, how does its weight change?

A) It is halved
B) It is doubled
C) It becomes four times greater
D) It remains the same

Answer: B) It is doubled.
Explanation: Weight is the force exerted by gravity on an object and is proportional to its mass. Doubling the mass of an object will double its weight.

13. The gravitational force between two bodies is 10 N. If the distance between them is doubled, what is the new force?

A) 40 N
B) 10 N
C) 2.5 N
D) 5 N

Answer: C) 2.5 N.
Explanation: The gravitational force is inversely proportional to the square of the distance between the bodies. If the distance is doubled, the force becomes 122=14\frac{1}{2^2} = \frac{1}{4}221=41 of the original force, so the new force is 2.5 N.

14. The Earth’s gravitational field strength decreases with?

A) Increasing mass
B) Increasing altitude
C) Decreasing altitude
D) Increasing distance from the Sun

Answer: B) Increasing altitude.
Explanation: The gravitational field strength decreases as the altitude (or distance from the center of the Earth) increases.

15. The gravitational force between two objects is directly proportional to?

A) The square of the distance between them
B) The product of their masses
C) The sum of their masses
D) The velocity of the objects

Answer: B) The product of their masses.
Explanation: According to Newton’s law of gravitation, the gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

16. The acceleration due to gravity at a point 4 times the Earth’s radius from its center is?

A) g4\frac{g}{4}4g
B) g16\frac{g}{16}16g
C) g2\frac{g}{2}2g
D) ggg

Answer: B) g16\frac{g}{16}16g.
Explanation: The gravitational force (and thus acceleration due to gravity) decreases with the square of the distance from the center of the Earth. At a distance 4 times the Earth’s radius, the acceleration due to gravity becomes g42=g16\frac{g}{4^2} = \frac{g}{16}42g=16g.

17. The gravitational field strength at a point in space is defined as?

A) The force per unit charge
B) The force per unit mass
C) The potential energy per unit mass
D) The velocity per unit mass

Answer: B) The force per unit mass.
Explanation: Gravitational field strength is the force exerted on a unit mass at a particular point in space. It is measured in N/kg.

18. If a satellite is in a stable orbit, its kinetic energy is?

A) Zero
B) Equal to its potential energy
C) Twice its potential energy
D) Equal to half its total mechanical energy

Answer: D) Equal to half its total mechanical energy.
Explanation: In a stable orbit, the kinetic energy of the satellite is equal to half of its total mechanical energy, with the other half being the gravitational potential energy.

19. If the radius of the Earth were to suddenly double, the acceleration due to gravity at the Earth’s surface would become?

A) Half
B) Double
C) One-fourth
D) One-eighth

Answer: A) Half.
Explanation: The acceleration due to gravity is inversely proportional to the square of the radius. If the radius of the Earth doubles, the acceleration due to gravity becomes 122=14\frac{1}{2^2} = \frac{1}{4}221=41, so the new acceleration due to gravity would be half.

20. The period of revolution of a satellite depends on?

A) The mass of the satellite
B) The radius of the satellite’s orbit
C) The gravitational constant
D) Both B and C

Answer: D) Both B and C.
Explanation: The period of revolution of a satellite in orbit depends on the radius of the orbit and the gravitational constant. It is governed by Kepler’s third law, which relates orbital period to orbital radius.

21. The universal law of gravitation was formulated by?

A) Galileo Galilei
B) Albert Einstein
C) Isaac Newton
D) Johannes Kepler

Answer: C) Isaac Newton.
Explanation: Isaac Newton formulated the universal law of gravitation in 1687, stating that every particle in the universe attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.

22. The weight of an object is the force of gravity acting on it. If the object is taken to a height where the gravitational force is one-quarter of its value on the Earth’s surface, its weight will be?

A) The same
B) Double
C) One-quarter
D) Half

Answer: C) One-quarter.
Explanation: The gravitational force at a height above the Earth’s surface decreases as the square of the distance from the Earth’s center. At a height where the gravitational force is one-quarter of its value, the weight of the object will also be one-quarter.

23. Gravitational potential energy at the surface of Earth is?

A) Positive
B) Negative
C) Zero
D) Infinite

Answer: B) Negative.
Explanation: Gravitational potential energy is taken as zero at infinity, and it becomes negative as the object approaches the Earth due to the attractive nature of gravity.

24. A body is in a free fall. Its potential energy decreases. Which of the following is true?

A) Its kinetic energy increases
B) Its velocity decreases
C) Its mass increases
D) Its height increases

Answer: A) Its kinetic energy increases.
Explanation: As a body falls freely towards the Earth, its potential energy decreases, and this lost potential energy is converted into kinetic energy, which increases.

25. The gravitational field strength at a point 3 times the Earth’s radius from its center is?

A) g9\frac{g}{9}9g
B) g3\frac{g}{3}3g
C) g6\frac{g}{6}6g
D) g4\frac{g}{4}4g

Answer: A) g9\frac{g}{9}9g.
Explanation: Gravitational field strength is inversely proportional to the square of the distance from the Earth’s center. So, at 3 times the Earth’s radius, the field strength will be g32=g9\frac{g}{3^2} = \frac{g}{9}32g=9g.

26. If the radius of a planet is halved, what happens to its escape velocity?

A) It is halved
B) It is doubled
C) It becomes four times greater
D) It remains unchanged

Answer: B) It is doubled.
Explanation: Escape velocity is directly proportional to the square root of the radius. If the radius is halved, the escape velocity will increase by a factor of 2\sqrt{2}2, i.e., it will be doubled.

27. The centripetal force on a satellite in orbit is provided by?

A) The gravitational force
B) The magnetic force
C) The frictional force
D) The electric force

Answer: A) The gravitational force.
Explanation: The gravitational force provides the necessary centripetal force to keep a satellite in orbit around a planet.

28. The gravitational potential energy of an object at a height hhh from the Earth’s surface is given by?

A) mghmghmgh
B) 12mgh2\frac{1}{2}mgh^221mgh2
C) mgh2mgh^2mgh2
D) GMmh\frac{GMm}{h}hGMm

Answer: A) mghmghmgh.
Explanation: The gravitational potential energy of an object near the Earth’s surface is given by U=mghU = mghU=mgh, where mmm is the mass, ggg is the acceleration due to gravity, and hhh is the height above the surface.

29. A body is projected vertically upwards. What happens to its gravitational potential energy as it rises?

A) It remains constant
B) It decreases
C) It increases
D) It first decreases, then increases

Answer: C) It increases.
Explanation: As the body rises, its height increases, so its gravitational potential energy increases because it is farther from the Earth’s surface.

30. If the distance between two bodies is reduced by half, the gravitational force between them becomes?

A) Four times greater
B) Twice as large
C) Half as large
D) One-fourth as large

Answer: A) Four times greater.
Explanation: Gravitational force is inversely proportional to the square of the distance between the two bodies. If the distance is halved, the gravitational force becomes 22=42^2 = 422=4 times greater.

31. The energy needed to launch an object from the Earth’s surface to infinity is equal to?

A) The object’s kinetic energy
B) The object’s gravitational potential energy
C) The object’s total mechanical energy
D) The object’s escape energy

Answer: D) The object’s escape energy.
Explanation: The energy required to launch an object from the Earth’s surface to infinity is the escape energy, which is equal to the magnitude of the gravitational potential energy at the Earth’s surface.

32. The gravitational field at the center of the Earth is?

A) Zero
B) Maximum
C) Minimum
D) Infinite

Answer: A) Zero.
Explanation: The gravitational field strength at the Earth’s center is zero because the forces from all parts of the Earth cancel each other out due to symmetry.

33. The period of a simple pendulum depends on?

A) The mass of the bob
B) The length of the string and the acceleration due to gravity
C) The amplitude of the swing
D) The temperature of the environment

Answer: B) The length of the string and the acceleration due to gravity.
Explanation: The period of a simple pendulum is given by T=2πLgT = 2\pi \sqrt{\frac{L}{g}}T=2πgL, where LLL is the length of the string and ggg is the acceleration due to gravity.

34. The gravitational force between two objects is FFF. If the distance between them is halved, the force between them becomes?

A) 2F2F2F
B) 4F4F4F
C) F/2F/2F/2
D) F/4F/4F/4

Answer: B) 4F4F4F.
Explanation: Gravitational force is inversely proportional to the square of the distance between two objects. If the distance is halved, the force becomes (22)=4(2^2) = 4(22)=4 times stronger.

35. Which of the following is true about the escape velocity?

A) It is independent of the mass of the object.
B) It increases with increasing height from the Earth’s surface.
C) It is independent of the mass of the planet.
D) It decreases with decreasing radius of the planet.

Answer: A) It is independent of the mass of the object.
Explanation: Escape velocity depends on the mass and radius of the planet but not on the mass of the object. The escape velocity is given by v=2GMRv = \sqrt{\frac{2GM}{R}}v=R2GM, where MMM is the mass of the planet and RRR is the radius of the planet.

36. A person weighs 600 N on Earth. What will be their weight on a planet where the gravitational field is twice as strong?

A) 300 N
B) 600 N
C) 1200 N
D) 2400 N

Answer: C) 1200 N.
Explanation: The weight of an object is directly proportional to the gravitational field strength. If the gravitational field is twice as strong, the weight will also double, i.e., 600 N×2=1200 N600 \, \text{N} \times 2 = 1200 \, \text{N}600N×2=1200N.

37. Which of the following is not a consequence of gravitational force?

A) The Earth’s revolution around the Sun
B) The Moon’s orbit around the Earth
C) The force that keeps the atmosphere bound to Earth
D) The force that allows the rocket to launch into space

Answer: D) The force that allows the rocket to launch into space.
Explanation: Gravitational force acts on all objects, but a rocket’s launch is primarily due to the force generated by its engines, not the gravitational force itself. The gravitational force is a hindrance to launching a rocket, which requires overcoming Earth’s gravity.

38. The gravitational field strength at a height hhh above the Earth’s surface is given by?

A) g(1+h/R)2\frac{g}{(1 + h/R)^2}(1+h/R)2g
B) g(1−h/R)2\frac{g}{(1 – h/R)^2}(1−h/R)2g
C) gh2\frac{g}{h^2}h2g
D) gh\frac{g}{h}hg

Answer: A) g(1+h/R)2\frac{g}{(1 + h/R)^2}(1+h/R)2g.
Explanation: The gravitational field strength at a height hhh above the Earth’s surface is given by g′=g(1+h/R)2g’ = \frac{g}{(1 + h/R)^2}g′=(1+h/R)2g, where RRR is the radius of the Earth.

39. The escape velocity of an object is the velocity required to?

A) Overcome the gravitational pull of the planet
B) Reach the maximum height in a projectile motion
C) Leave the atmosphere of the planet
D) Overcome air resistance

Answer: A) Overcome the gravitational pull of the planet.
Explanation: Escape velocity is the minimum speed needed for an object to break free from a planet’s gravitational influence without further propulsion.

40. The gravitational potential energy of a system is always?

A) Positive
B) Zero
C) Negative
D) Infinite

Answer: C) Negative.
Explanation: Gravitational potential energy is taken to be zero at infinity. As objects come closer to a massive body, their potential energy becomes more negative because gravity does work on them.

41. What would happen to the weight of an object at the Earth’s equator compared to the poles?

A) It would be greater at the poles.
B) It would be greater at the equator.
C) It would be the same everywhere.
D) It would be zero everywhere.

Answer: A) It would be greater at the poles.
Explanation: Due to the Earth’s equatorial bulge, the distance from the center of the Earth is greater at the equator than at the poles. Since gravity decreases with distance from the Earth’s center, the gravitational force (and thus weight) is greater at the poles.

42. The gravitational potential energy of an object on the Earth’s surface is?

A) Zero
B) Positive
C) Negative
D) Infinite

Answer: C) Negative.
Explanation: Gravitational potential energy is zero at infinity. Near the Earth’s surface, it is negative because the object is in the gravitational field of Earth.

43. The escape velocity at the surface of a planet is given by?

A) GMR\sqrt{\frac{GM}{R}}RGM
B) GMR\frac{GM}{R}RGM
C) GM2R\frac{GM}{2R}2RGM
D) GMR2\sqrt{\frac{GMR}{2}}2GMR

Answer: A) GMR\sqrt{\frac{GM}{R}}RGM.
Explanation: Escape velocity vev_eve is given by ve=2GMRv_e = \sqrt{\frac{2GM}{R}}ve=R2GM, where MMM is the mass of the planet and RRR is its radius.

44. If a planet has the same mass as Earth but twice the radius, the escape velocity will?

A) Be the same
B) Be twice as large
C) Be half as large
D) Be four times as large

Answer: C) Be half as large.
Explanation: Escape velocity depends on the square root of the inverse of the radius. If the radius is doubled, the escape velocity is reduced by a factor of 2\sqrt{2}2, so it will be approximately half as large.

45. A satellite is in a circular orbit around the Earth. The gravitational force acting on it provides?

A) The necessary centripetal force
B) The necessary frictional force
C) The necessary tension
D) The necessary thrust

Answer: A) The necessary centripetal force.
Explanation: The gravitational force between the Earth and the satellite acts as the centripetal force that keeps the satellite in orbit.

46. The period of revolution of a satellite in orbit depends on?

A) Its mass
B) The mass of the planet it orbits
C) The distance from the planet’s center
D) Both B and C

Answer: D) Both B and C.
Explanation: The period of revolution of a satellite depends on the mass of the planet and the distance from the planet’s center. According to Kepler’s third law, T2∝R3T^2 \propto R^3T2∝R3, where RRR is the orbital radius.

47. The gravitational field strength at the surface of the Earth is?

A) 9.8 N/kg9.8 \, \text{N/kg}9.8N/kg
B) 9.8 N/m²9.8 \, \text{N/m²}9.8N/m²
C) 9.8 m/s²9.8 \, \text{m/s²}9.8m/s²
D) 10 N/kg10 \, \text{N/kg}10N/kg

Answer: A) 9.8 N/kg9.8 \, \text{N/kg}9.8N/kg.
Explanation: The gravitational field strength at the Earth’s surface is 9.8 N/kg9.8 \, \text{N/kg}9.8N/kg, which is equivalent to the acceleration due to gravity.

48. What happens to the gravitational potential energy of a satellite as it moves farther from Earth?

A) It increases
B) It decreases
C) It remains the same
D) It becomes zero

Answer: B) It decreases.
Explanation: As the satellite moves farther from Earth, its gravitational potential energy becomes more negative, indicating a decrease in the potential energy.

49. Which of the following is the correct formula for gravitational potential energy near the Earth’s surface?

A) U=mghU = mghU=mgh
B) U=GMmhU = \frac{GMm}{h}U=hGMm
C) U=GMmr2U = \frac{GMm}{r^2}U=r2GMm
D) U=GMmRU = \frac{GMm}{R}U=RGMm

Answer: A) U=mghU = mghU=mgh.
Explanation: The gravitational potential energy near the Earth’s surface is given by U=mghU = mghU=mgh, where mmm is the mass, ggg is the gravitational field strength, and hhh is the height above the Earth’s surface.

50. Which of the following is an effect of gravity on Earth?

A) Formation of tides
B) Creation of light waves
C) Reflection of light
D) Reflection of sound waves

Answer: A) Formation of tides.
Explanation: Gravity from the Moon and the Sun causes the formation of tides on Earth. The gravitational pull of the Moon and the Sun on the Earth’s oceans leads to the periodic rise and fall of sea levels.

These Unit 6: Gravitation MCQs should now provide a comprehensive understanding of the topic, ranging from fundamental concepts to more advanced applications.