Question

A stone is projected at angle x with the horizontal from the roof of a tall building falls on the ground after three seconds.Two seconds after the projection it was again at the level of projection.find the height of the building?

Answer 1

Time taken to reach maximum height after projection is :

T = (U sin x) / g

The maximum height reached is :

H = (U² Sin²x) / 2g

Time taken for the free fall is :

3 - (U sin x) / g

Free fall %

S = ut + 0.5gt²

U = 0

S = 0. 5 × (3 - (U sin x) / g) ²

This gives the total height.

The height of the building is :

Total height less the maximum projectile height :

{0.5/g (3- U sin x) ²} - {(V²Sin²x) / 2g}