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.