# Homework Help: 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?