Help Free Fall Problem

1. Sep 5, 2004

shawonna23

Help!! Free Fall Problem

A pellet gun is fired straight downward from the edge of a cliff that is 13 m above the ground. The pellet strikes the ground with a speed of 30 m/s. How far above the cliff edge would the pellet have gone had the pellet been fired straight upward?

2. Sep 5, 2004

Tide

What have you done so far?

3. Sep 5, 2004

shawonna23

I started using the equation :

y=-1/2 gt^2-30t+0

4. Sep 5, 2004

veryyoung

are you assuming that 30 m/s is not the pellets terminal velocity?

5. Sep 5, 2004

Tide

Have you learned about energy conservation yet? If so then you can use it to find what the "muzzle velocity" is. Basically it says that $\frac{1}{2}mv^2_{final} - mg \times 30 = \frac{1}{2}mv^2_{initial}$, i.e. potential + kinetic energy is constant.

6. Sep 5, 2004

shawonna23

yes, i'm assuming that 30m/s is not the pellets terminal velocity

7. Sep 5, 2004

pervect

Staff Emeritus
Hmmm, that's not the right equation - did you understand the remarks Tide made about energy conservation?