Question

a body is thrown from height of 200m at 15m/s. find thetime required for the body
to strike the ground if its initial velocity directed 1. upwards 2. downwards. find the
velocity with which it hits the ground g=10m/s

Answer 1

When the ball reaches the highest point, its velocity will be zero. So final velocity is v=0m/s

Here, the time to reach highest point is equal to time to hit ground from highest point.

Consider upward motion, the acceleration of the ball is a=−g=−9.8m/s

2

(minus for motion opposite to gravity)

If t be the required time.

Using v=u+at,

0=25+(−9.8)t

⟹ t=2.5s

Thus the ball hits the ground after 2.5 seconds after reaching its highest point.