Question

A ball is thrown upward with a velocity of 100 m s it will reach the ground after

Answer 1

velocity=100m/s(initial)
final velocity =0

v^2-u^2=2(-g)×s
0-100×100=-2×10×s
s=500m

time taken from going bottom to top
=500/100=5sec

time for overall journey=5sec(going up)+5sec(coming down)=10sec.

so answer is 10 sec.
hope this will help you.

Answer 2

short n easy go to formula V=at
here v=100 a is due to gravity that 10 n t=?
whereas 100=10×t
100/10=t
t=10