A ball is thrown vertically upwards with a speed of 10 m s -1 from the top of a tower 200 m high and another is thrown vertically downwards with the same speed simultaneously. The time difference between them in reaching the ground in seconds is (Take .g=10 m s -2)

Question

A ball is thrown vertically upwards with a speed of 10 m s -1 from the top of a tower 200 m high and another is thrown vertically downwards with the same speed simultaneously. The time difference between them in reaching the ground in seconds is (Take .g=10 m s -2) (A) 12 (B) 6 (C) 2 (D) 1

Tardigrade Admin · Accepted Answer

As the ball thrown vertically upwards will come back to the point of projection with the same speed, both the balls will move downwards with same initial velocity, so both will hit ground with velocity v=√u2+2 g h. However, the ball projected up will take (2 u/g)(=2 × (10/10)=2 s ) time more to reach the ground than the ball projected downwards.

Q. A ball is thrown vertically upwards with a speed of 10ms−1 from the top of a tower 200 m high and another is thrown vertically downwards with the same speed simultaneously. The time difference between them in reaching the ground in seconds is (Take g=10ms−2)

12

6

2

1

Q. A ball is thrown vertically upwards with a speed of $10 m s^{- 1}$ from the top of a tower 200 m high and another is thrown vertically downwards with the same speed simultaneously. The time difference between them in reaching the ground in seconds is (Take $g = 10 m s^{- 2})$