Free Gravitation MCQs with Answers

41. The formula used by Cavendish to find out the value of G with the help of "Cavendish apparatus" was:

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

Explanation: The formula used by Cavendish to find out the value of G with the help of "Cavendish apparatus" was G = Cθr2/Mml.

42. When the downward acceleration of the elevator increased, the weight of the objects inside it will:

• A. Decrease
• B. Increase
• C. Remain the same
• D. None of these

Explanation: The weight of an object is the force exerted on it due to gravity. On Earth, this force is usually equal to the gravitational force, and the weight is given by the formula: Weight=mass×gravitational acceleration If an elevator is accelerating downward, there is an additional force acting on the objects in the upward direction, which is the force they experience due to the acceleration. In this case, the net force acting on the objects is the difference between the gravitational force and the force due to acceleration. When the elevator accelerates downward, the net force acting on the objects is less than their weight alone (gravitational force), so the apparent weight of the objects decreases. This can create a feeling of reduced weight for the objects and occupants inside the elevator.

43. The force with which the earth attracts a body is its:

• A. Weight
• B. Mass
• C. Density
• D. Gravitational acceleration

Explanation: The force with which the Earth attracts a body is referred to as its weight. Weight is a force acting on an object due to gravity. It is the force with which an object is pulled towards the center of the Earth (or any other celestial body).

44. The value of gravitational acceleration at the surface of the earth is:

• A. 8.9 ms-2
• B. 8.8 ms-2
• C. 9.8 ms-2
• D. 1.98 ms-2

Explanation: The value of gravitational acceleration at the surface of the earth is 9.8 ms -2

45. The value of g at a depth of x metres from the surface of the earth is calculated from the formula:

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

Explanation: The value of g at a depth of x metres form the surface of the earth is calculated from the formula g = GMe/(Re - x)2

46. As we go below the surface of the earth, the value of g:

• A. Increases
• B. Decreases
• C. Remains constant
• D. Has no value

Explanation: As you go below the surface of the Earth, the value of gravitational acceleration (g) generally decreases. This is because gravitational acceleration is inversely proportional to the distance from the center of the Earth.

47. At the centre of the earth, the value of g becomes:

• A. Zero
• B. Infinity
• C. 9.8 ms-2
• D. None of the above

Explanation: At the center of the Earth, the value of gravitational acceleration (g) becomes zero. This is because, at the center, the mass above cancels out the gravitational forces from all directions, resulting in a net gravitational force of zero.

48. An astronaut, in a satellite, orbiting the earth, experience a state of weightlessness because of:

• A. The satellite orbits the earth at a very large speed
• B. The satellite orbits the earth with a centripetal acceleration greater than 'g'
• C. The satellite orbits the earth with a centripetal acceleration less than 'g'
• D. The satellite orbits the earth with a centripetal acceleration equal to 'g'

Explanation: When a satellite is in orbit around the Earth and moving at the right speed, it is in free fall towards the Earth, and its acceleration due to gravity is exactly balanced by the centripetal acceleration needed to keep it in orbit. This results in a state of weightlessness for the astronaut inside the satellite.

49. Practically the inertial mass and the gravitational mass are:

• A. Additive inverse of each other
• B. Multiplicative inverse of each other
• C. Equal
• D. Not equal

Explanation: Practically, the inertial mass and the gravitational mass are observed to be equal. This equality is a fundamental assumption in classical mechanics and is essential for the consistency of the laws of motion and gravitation.

50. When a lift is moving upward with a uniform velocity, the apparent weight of a body inside the lift will be:

• A. Equal to its actual weight
• B. Less than the actual weight
• C. More than the actual weight
• D. Zero

Explanation: When a lift is moving upward with a uniform velocity, the apparent weight of a body inside the lift is equal to its actual weight. This is because the forces acting on the body, including gravity and the lift's acceleration, are balanced, resulting in no net force affecting the body's weight.