a boy drops a stone from the top of a building 100m high another boy throws an iron ball, - Science - Gravitation

Question

a boy drops a stone from the top of a building 100m high another
boy throws an iron ball, with certain velocity, 2 second later the
stone was dropped calulate the velocity with which iron ball was
thrown , so that both the ball and the stone strike the ground at
the same time

Somnath physics · Accepted Answer

Hi,
For the stone that is dropped,
Initial velocity, u = 0
Distance covered, h = -100 m
Acceleration due to gravity, g = -10 ms-2

So, the stone reach the ground in 4 5 s after it is
dropped
Now, at t = 0, the iron ball is thrown
At, t = 2 s, the stone is dropped
So, the stone reach the ground at t = 2 + 4 5 = 6 5 s
Which means the iron ball was in air for 6 5 s
For the iron ball,
Initial velocity is say, v
Final velocity will be â€“v
Acceleration due to gravity, g = -10 ms-2
Time of flight, t = 6 5 s

So, the iron ball has to be thrown at a speed 32 5 m/s to make
both the projectiles reach the ground at the same time

a boy drops a stone from the top of a building 100m high. another boy throws an iron ball, with certain velocity, 2 second later the stone was dropped. calulate the velocity with which iron ball was thrown , so that both the ball and the stone strike the ground at the same time.