Question

A stone projected at an angle of 60º from the ground level strikes at an angle of 30º on the roof of a building of height ‘h’. Then the speed of projection of the stone is : 

Answer 1

Correct option (C)

Explanation:

Let initial and final speeds of stone be u and v. 

∴ v² = u² – 2gh .........(1) 

and v cos 30° = u cos 60° ..........(2) 

solving 1 and 2 we get 

u = √(3gh)