Question

A stone is projected at an angle of 60° from the ground level at an angle of 30 degree strikes on roof of building of height h is equal to 30 m find speed of projection of stone

Answer 1

Components in x and y direction of initial velocity with 60 degree are:

ucos60 and usin60 respectively.

At h height distance,

tan30 = Vy/ucos60

Vy = u/2root3

Further Distance in y – direction :

Vy^2 – (usin60)^2 = 2as

(u/2root3)^2 – (uroot3/2)^2  = -2gs

On solving we get,

u = root(3gh)

that is (C) option.