Question

A riffle shoots a bullet with a muzzle velocity 100m/s at a small target 200m away.How high above the target must the riffle be aimed do that the bullet will hit the ground?

Answer 1

time taken to reach by bullet 200m away from initial position is t = 200/100 = 2sec.

now, here vertical initial speed = 0
vertical acceleration, a = acceleration due to gravity

so, use formula, S = ut + 1/2at² for vertical component.
s = 0 + 1/2 at²

s = 0 + 1/2 × 10 × 2²

s = 20m

hence, 20m above the target must the riffle be aimed do that the bullet will hit the ground