# Projectile Motion Review Work Check

1. Apr 19, 2010

### jacksonpeeble

1. The problem statement, all variables and given/known data
A 4kg object is fired with a horizontal velocity of 8 m/s from a cliff 122.5 meters high. a) How long does it take the projectile to hit the ground? b) How far from the base of the cliff does it land? c) What is its speed right before hitting the ground? d) What is the direction of the velocity right before hitting the ground?

2. Relevant equations
d=.5at2
vf=vi+at
vh=dh/t
a = acceleration = 9.8 m/s/s (down)
d = distance (dh = 122.5 m)
t = time
v = velocity (vi=8 m/s horizontal)

3. The attempt at a solution
a. d=.5at^2 = 122.5=.5*9.8*t^2, t=5 seconds
b. d=v0t+.5at^2 = d=8*5+.5*9.8*5^2, d=162.5 meters
c. vf^2=vi^2+2ad = vf^2=8^2+2*9.8*162.5, vf=57 m/s
d. tan^-1(162.5/122.5)=52.99 degrees

I believe I have done all of the work correctly, but the unit was a long time ago, so I'd greatly appreciate confirmation or corrections if necessary, since the review assignment is worth a significant amount of points.

Thank you very much in advance for any help!

2. Apr 19, 2010

### jacksonpeeble

Any input? If all is correct (which I'm not entirely sure of), I'd appreciate verification, too!