Free Gravitation MCQs with Answers

51. When the lift is moving upward with a uniform acceleration, the apparent weight of the body inside it will be:

• A. Less than its actual weight
• B. More than its actual weight
• C. Varying with velocity
• D. The same as its actual weight

Explanation: When the lift is moving upward with a uniform acceleration, the apparent weight of the body inside it will be more than its actual weight. This is because the normal force (which contributes to the apparent weight) is greater than the actual weight due to the upward acceleration.

52. When the lift moves upward with a uniform acceleration "a", the apparent value of g inside the lift changes to:

• A. g + a
• B. g - a
• C. g - 2a
• D. g + 2a

Explanation: When the lift moves upward with a uniform acceleration a, the apparent weight experienced by a person inside the lift is given by the equation W =m(g+a), where m is the mass of the person, g is the acceleration due to gravity, and a is the uniform acceleration of the lift.The apparent weight is the force experienced by the person, and in this case, it includes both the force due to gravity (m⋅g) and the additional force due to the upward acceleration of the lift (m⋅a).

53. When the lift moves downward with a uniform acceleration, the apparent weight of the body inside the lift will be:

• A. Less than its actual weight
• B. More than its actual weight
• C. Varying with its velocity
• D. The same as its actual weight

Explanation: If the lift is moving downward with a uniform acceleration, there is an additional force acting on the body in the upward direction, opposing the force of gravity. This reduces the net force acting on the body and, consequently, its apparent weight. The apparent weight is given by the formula: Apparent Weight=Actual Weight−Force due to Acceleration Since the force due to acceleration acts in the opposite direction of gravity, it subtracts from the actual weight, making the apparent weight less than the actual weight.

54. When the lift moves downward with an acceleration "a", the apparent value of "g" inside the lift changes to:

• A. g + a
• B. g - a
• C. g - 2a
• D. g + 2a

Explanation: The apparent weight is the force experienced by an object inside the lift, and it's the force with which the object presses against the floor of the lift. When the lift is moving downward with acceleration a, the effective acceleration acting on the object is g−a because the acceleration due to gravity (g) is partially opposed by the acceleration of the lift (a).

55. When the lift falls with an acceleration equal to "g", the apparent weight of an object inside it will:

• A. Remain the same
• B. Become half
• C. Become zero
• D. Become double

Explanation: In free fall, the lift and everything inside it are accelerating downward at the same rate as gravity. In this scenario, there is no contact force (normal force) acting on the object; it is essentially in a state of weightlessness. As a result, the object experiences zero apparent weight, and it will feel as if it is in a state of weightlessness, just like astronauts in free fall during space travel.

56. The weight of a body on moon is _ of its weight on earth:

• A. One fourth
• B. One sixth
• C. One eighth
• D. One third

Explanation: The explanation is given below: The weight of a body on the moon is approximately one-sixth (1/6) of its weight on Earth. This is due to the difference in gravitational acceleration on the moon compared to Earth. The gravitational acceleration on the moon is about 1/6th of the gravitational acceleration on Earth.

57. The astronauts in a satellite experience a state of weightlessness because both the astronaut and the satellite fall toward the earth with an acceleration of:

• A. g
• B. 2g
• C. 3g
• D. -g

Explanation: The sensation of weightlessness experienced by astronauts in a satellite is due to the fact that both the satellite and the astronauts are in free fall toward the Earth. This free fall is caused by the gravitational force between the Earth and the satellite. The acceleration experienced by both the satellite and the astronauts is the acceleration due to gravity, denoted by 'g.' Thus, A is the correct option.

58. In a spaceship, artificial gravity is created with the help of:

• A. Centripetal force
• B. Centrifugal force
• C. Magnetic force
• D. None of the above

Explanation: Correct Answer: B Artificial gravity in a spaceship can be created using the principle of centripetal force. This force is generated by the rotation of the spaceship. When a spaceship rotates, it creates a centrifugal force that pushes objects inside the spaceship outward, away from the axis of rotation. This outward force acts as if it were a gravitational force, creating a sense of gravity for the occupants inside. The formula for centripetal force (Fc) is given by: Fc =m⋅v2/r In the case of a rotating spaceship, the floor of the spaceship acts as the "ground," and the centrifugal force experienced by objects on the floor provides a sense of gravity. The greater the rotation speed or the larger the radius of rotation, the stronger the artificial gravity effect.

59. The frequency of a spaceship of radius R revolving around its axis to provide a force of gravity equal to the weight of the astronauts on earth, should be:

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Explanation: Correct Option: B The numerical explanation is given as follows:

60. How the artificial gravity is created in a satellite to overcome the state of weightlessness experienced by the astronaut in it?

• A. By increasing the orbital speed of the satellite
• B. By decreasing the orbital speed of satellite
• C. By keeping the orbital speed of the satellite constant equal to that of the earth's around sun
• D. By causing the satellite to spin about its own axis

Explanation: Artificial gravity in a spaceship can be created using the principle of centripetal force. This force is generated by the rotation of the spaceship. When a spaceship rotates, it creates a centrifugal force that pushes objects inside the spaceship outward, away from the axis of rotation. This outward force acts as if it were a gravitational force, creating a sense of gravity for the occupants inside.