Question

A rock thrown up into the air with an initial speed of 25 m/s . How much time will pass before the rock is moving back down at 6 m/s ?

Answer 1

To reach the highest point it will take time t
v= u + at
0 = 25 -9.8t
time t = 25/9.8 = 2.55 seconds

On the way down
v = u + at
6 = 9.8 t

time t= 6/9.8 = 0.61 seconds

Total time = 2.55 + 0.61 = 3.16 seconds