Question

A projectile is fired with an initial velocity of 98 m/s at an angle 30o to the horizontal. if it strikes the top of a hill after 5 s, what is the elevation of the hill above the point of firing

Answer 1

Intitial Velocity, u = 98m/s
The vertical component of the velocity will be = u*sin30° = 98 * 1/2 = 49m/s

The height of the projectile will depend on the vertical component and not on the horizontal component . 

Here the acceleration will be gravity, g.

s = ut + 1/2 at²
= 49 * 5 - 1/2 *10 * 25
= 120m

so the height of the hill is 120m above the point of firing