Motion Under Gravity (Physics)

Total Questions: 41

11. The two balls of iron and wood of same weight dropped from the same height in air then - [U.P.P.C.S. (Pre) 1992]

Correct Answer: (c) The wooden ball falls later
Solution:If there is no resistance from the air, both the balls will hit the ground at the same time. But in the presence of air, the iron ball falls first because of its smaller size and wood ball falls later because of its larger size. The resistance from air slows down the fall of larger thing with same weight. So, option (c) will be the correct answer.

12. Two balls A and B are of 10 kg. and 1 kg. respectively. They are dropped simultaneously from the height of 20 m. which of the following is correct ? [U.P. Lower Sub. (Pre)]

Correct Answer: (c) Both A and B will reach the ground at the same time
Solution:

13. Two objects of different masses falling near the surface of the Moon would : [69th B.P.S.C. (Pre) 2023]

Correct Answer: (c) have same velocity at any instant
Solution:The question does not give the parameters for height and time. Assuming that both objects are dropped at the same time from the same reasonable height, they will have 'the same velocity at any instant' as they fall freely near the surface of the moon.

14. Assertion (A) : The weight of the human being on the Moon is 1/6 in the comparison to Earth. [Chhattisgarh P.C.S. (Pre) 2008]

Reason (R) : The Moon does not have gravity like Earth.

Select the answer from following codes-

Correct Answer: (c) (A) is true but (R) is false.
Solution:The Moon is the Earth's only natural satellite. The surface gravity of the Moon is only 1/6 that of the Earth. So the weight of human being on the Moon will be 1/6 of that on the Earth. Hence, assertion is true, but reason is false.

15. The weight of anybody is - [U.P.P.C.S. (Mains) 2009, (Pre) 2006]

Correct Answer: (b) Maximum at poles
Solution:

16. The weight of human body is - [U.P.P.C.S. (Mains) 2015]

Correct Answer: (a) Maximum at the poles.
Solution:

17. If the spinning speed of the Earth increases, then the weight of the body at the equator will : [67th B.P.S.C. (Pre) (Re.Exam) 2022]

Correct Answer: (b) decrease
Solution:

The weight of a body on the Earth is the amount of gravitational pull on it exerted by the Earth. Due to Earth's rotation, centrifugal force also exerted on a body on Earth, which tries to move the body away from the centre of the Earth. At the equator, centrifugal force is maximum as the velocity of rotation is maximum at the equator of the Earth.

Thus, at the equator, centrifugal force acts against gravity to reduce the weight of the body. With the increase in the speed of rotation of the Earth, the centrifugal force at equator will increase and the weight of the body will seem to have decreased.

18. The variation of displacement d with time t in the case of a particle falling freely under the gravity from rest is correctly shown in the graph. [I.A.S. (Pre) 1996]

Correct Answer: (a)
Solution:

19. A smooth plane inclined at an angle θ with the horizontal as shown in the given figure. A body starts from rest and slides down on the inclined surface. The time taken by the body to reach the bottom is-

Correct Answer: (c)
Solution:

20. A ball is dropped from the top of a high building with a constant acceleration of 9.8 m/s².what will be its velocity after 3 seconds? [I.A.S. (Pre) 1998]

Correct Answer: (c) 29.4 m/s
Solution:

According to Question,

a = 9.8 m/s², t = 3 sec., u - 0

we known that, v = u + at = 0 + 9.8 × 3 = 29.4 m/s.