Free Gravitation MCQs with Answers

161. The apparent weight of a man in an elevator moving up with acceleration, a, is:

• A. mg
• B. mg+ma
• C. mg - ma
• D. mg/2

Explanation: As the escalator is moving upwards, the correct expression for apparent weight can be written as W' = m x (g + a)Hence the correct option is B where W'= mg+ma

162. If the distance between two bodies is doubled the gravitational force will:

• A. Remain same
• B. Become four times
• C. Increase four times
• D. Become one fourth

Explanation: F=GMm/R2 When the distance is doubled, F'= GMm/4R2On comparing both the forces their ratio is equal to F'/F= 1/4Hence the correct option is D.

163. If the distance between two masses is halved the gravitational force is:

• A. Halved
• B. Doubled
• C. Four times
• D. Same

Explanation: F=GMm/R2 When the distance is halved, F'= GMm/0.25R2 On comparing both the forces their ratio is equal to F'/F= 4/1Hence, the correct option is C.

164. Newton's law of Gravitation states that the force of attraction between the two bodies is inversely proportional to:

• A. Product of their masses
• B. Square of the distance between them
• C. Square of the distance between their centers
• D. Product of mass & distance between them

Explanation: F=GMm/R2 According to the formula, it is inversely proportional to the square of the separation of two bodies from their centers. Hence C is the correct option.

165. The gravitational force between two bodies is:

• A. Impulsive
• B. Reactive
• C. Repulsive
• D. Attractive

Explanation: D is correct. It is a matter of fact that Gravitational force is always an attractive force between two bodies.

166. Newton's law of Gravitation states that the force of attraction between two bodies is directly proportional to:

• A. Product of mass and distance between them
• B. Square of the distance between them
• C. Product of their masses
• D. Product of square of their masses

Explanation: C is correct. The force of attraction between two bodies is directly proportional to the products of their masses only. As, F= GMm/R2 .

167. Which force is responsible for the motion of falling bodies and the motion of planets around the Sun?

• A. Nuclear force
• B. Gravitational force
• C. Electrostatic force
• D. Electromagnetic force

Explanation: A is correct. Gravitational force is the only force that is responsible for the motion of falling bodies and the motion of planets around the Sun.

168. If law of gravitation is written in vector form with negative sign, then gravitational force is written as

• A. Attractive force
• B. Repulsive force
• C. Negative force
• D. None of these

Explanation: A is correct. -ve sign always shows attractive force.

169. The mass of Earth is given as:

• A. 6 x 10^24 kg
• B. 1.6 x 10^-30 kg
• C. 1.6 x 10^-31 kg
• D. None of the above

Explanation: A is correct. It is a fact that Earth's mass is 6 x1024 kg.

170. Mass per unit volume is called:

• A. Torque
• B. Density
• C. Viscosity
• D. None of these

Explanation: B is correct. Mass per unit volume is density.