Question

The ball is thrown upwards from a top of the tower 40m high with a velocity 10ms-1.Find the time when it strikes the ground(g=10ms-2)

Answer 1

so on the top of building t=2u/g
= 2*10/10
=2sec
then from the building to earth
v=u-gt
0=10-10t
10t=10
t=1sec
total time=3sec
so the time to return to ground is 3sec