Question

A body is projected vertically upwards with speed u from the top of a tower. It strikes at the ground with speed 3u. What is (a) height of tower and (b) time take by the body to reach at the ground?

Answer 1

(a) Let upwards be negative direction.
In vertical direction `v^(2)=u^(2)+2as`
Here `v=3u, u=-u, a=g, s=h`
`9u^(2)=u^(2)+2g(h)rArrh=(8u^(2))/(2g)=(4u^(2))/(g)`
(b) In vertical direction `v=u+atrArr3u=-u+gtrArrt=(4u)/(g)`