Question

A stone is thrown veticallly up with initial velocity u from the top of a tower . It reaches the ground with velocity 3u . The height of tower is

Answer 1

let mass of ball is M , and ball is at top of tower of height H

by energy conservation ,

1/2$1/2Mu^2+Mgh=1/2M(3u)^2$

from here we get $H=u^2/2$