Question

A stone projected at at an angleof 60'from the ground level strike at an angle of 30' on the roof of a building of hight h . than the speed of projection of the stone

Answer 1

Components of x is ucos60° and y is usin60°

At h height distance,

tan30° = Vy/ucos60°

Vy = u/2√3

Distance in y – direction :

Vy² – (usin60)² = 2as

(u/2√3)² – (u√3/2)² = -2gs

By this ,we get

u = √3gh

Answer 2

Answer:

30 m/s

Explanation:

Let u be the speed of projection and v be the speed at which the stone strikes the building.

Resolve the components of velocity

horizontal component : vcos30=ucos60 = u/2

( u = √3 v )

vertical component : vsin30

Newton's equation for vertical component :

v²(sin30)² = u²(sin60)² - 2(10)(30)

(u/√3)² (1/4) = 3u²/4 - 600

u²/12 = 3u²/4 - 600

8u²/12 = 600

u² = 900

u=30