A body is projected vertically up with velocity u from a tower. It reaches the ground with velocity nu. The height of the tower is `H=u^2/(2g)(n^2-1)`

Explanation

`v^(2)-u^(2)=2as, "Here u=u, v=nu, a=-g, s=-H"`
`(nu)^(2)-u^(2)=2gH `
`(n^(2)-1)u^(2)=2gH " "H=(u^(2))/(2g) (n^(2)-1)`