Free Gravitation MCQs with Answers

181. A bird resting on the floor of an air-tight box which is being carried by a boy, starts flying. The boy will feel that the box is now:

• A. Heavier in the beginning and lighter afterwards
• B. Lighter
• C. Shows no change in weight
• D. Heavier afterwards

Explanation: The Explanation for this question will be added soon!

182. The minimum velocity required to go out from Earth's gravitational pull is called:

• A. Terminal velocity
• B. Angular velocity
• C. Drift velocity
• D. Escape velocity

Explanation: Escape velocity is the minimum velocity required to go out from Earth's gravitational pull. Hence D is correct.

183. The force of attraction acts along the:

• A. Axis of rotation
• B. Line joining the interacting bodies
• C. Line perpendicular to the interacting bodies
• D. None of these

Explanation: The force of attraction is always along the line joining the interacting bodies, be it imaginary or real. Hence C is correct .

184. The range through which the gravitational force acts is:

• A. Limited to 1 x 10^-10 m
• B. Limited to 1 x 10^-2 m
• C. Extremely long
• D. about 1 x 10^5 m

Explanation: F =GMm/ r 2 , So this shows that F can be 0 only when the distance is infinite, proving that Gravitational forces have an extremely long range. So the correct option is C.

185. According to the law of Universal Gravitation:

• A. Every body in the universe attracts every other body
• B. The force of attraction is directly proportional to the product of their masses
• C. The force of attraction is inversely proportional to the square of their distance
• D. All of the above

Explanation: The correct option is D. F is always given by - GMm/r 2 . - sign shows that gravitational force is an attractive force. The formula shows that force is directly proportional to the product of masses and is inversely proportional to the square of their separation.

186. The acceleration due to gravity on the moon is 1/6th of that on Earth, what will be the mass of the body on the moon, if its mass on Earth is m:

• A. m/6
• B. 6m
• C. m
• D. m/3

Explanation: The correct option is C . Mass is always independent of gravitational acceleration and is constant.

187. The radius of a planet is 5 times the radius of Earth, but is of the same mass, so the value of g on the planet is:

• A. 5 g
• B. g/5
• C. g/20
• D. g/25

Explanation: Gravitational acceleration (g) on a planet depends on GM/ r2 As the radius of the planet is five times that of Earth, its g' = GM/ 25r2 Comparing both the value of g , their ratio = g'/g= 1/25 So the correct answer is option D.

188. Two masses 10 cm apart, attract each other with a force,f Newtons. When 5 cm apart, these masses will attract each other with a force (in Newtons) of:

• A. f/2
• B. f/4
• C. 4f
• D. 2f

Explanation: The gravitational force between two masses is given by Newton's law of gravitation, f= GMm/ r 2 Initially, the distance was 10cm so f= GMm/ (10 cm )2 As the separation between them decreased to 5 cm, the new force f' became = GMm/ (5 cm )2 On comparing both the forces, their ratio is equal to, f'/f= 4/1 So the correct option is C.

189. If the Earth were three times farther from the Sun than it is now, the gravitational force exerted on Earth by the sun would be:

• A. Three times
• B. Nine times
• C. One-ninth times
• D. One-third times

Explanation: The correct option is: C) One-ninth times The gravitational force (f) is given by GMm/r 2 . In this case, if the Earth were three times farther from the Sun, the new distance (r') would be three times the original distance. So F' will be GMm/9r2 on comapring F' with F , we get a ratio of 1/9. So, the gravitational force (F') would be one-ninth of the original force (F).

190. If the mass of the Earth becomes four times large, the value of 'g' will:

• A. Remain unchanged
• B. Becomes four times larger
• C. Be doubled
• D. Become sixteen times larger

Explanation: Gravitational acceleration= GM/R2 As the mass increases four times so g'= 4gHence the correct option is B.