# Homework Help: Questions about Projectiles

1. Oct 3, 2012

### Nubcake

I have a few questions about projectiles that I just want to verify that my calculations and working out is correct.

A bullet is fired horizontally from a rifle at 250 m s -1. after travelling 100m the bullet strikes a target

Calculate the time take for the bullet to strike the target
Calculate the downward component of velocity of the bullet when it strikes the target

S= ut

For the first one I did
100 = 250t
t =0.4 s

And the second
Since the initial vertical velocity is 0
u = 0
t = 0.4
a = 9.8

v = u + at
v = 0 + 9.8 x 0.4
v = 3.92 m s -1

Another question is

Simultaneously a ball is thrown horizontally from a height and another is dropped from rest at the same height , which ball hits the ground first?

Both balls hit the ground at the same time since the initial vertical velocity of both balls is 0 they both free fall with the same acceleration.

Are these answers right because I do not have the answers to them

2. Oct 3, 2012

### Staff: Mentor

Looks good to me.