# Homework Help: Recoil velocity - help!

1. Dec 5, 2007

### pdubb

The lead female character in the movie Diamonds Are Forever is standing at the edge of an offshore oil rig. As she fires the gun, she is driven back over the edge and into the sea. Suppose the mass of a bullet is 0.013 kg, and its velocity is +702 m/s. Her mass (including the gun) is 48 kg.

(a) What recoil velocity does she acquire in response to a single shot from a stationary position, assuming that no external force keeps her in place?

(b) Under the same assumption, what would be her recoil velocity if, instead, she shoots a blank cartridge that ejects a mass of 5.0 10-4 kg at a velocity of +702 m/s?

i know that you take (mass of the bulllet) x (velocity of the bullet) / (mass of the girl) to find the girl's velocity, and it equals -.19 for the first one but i dont know how to do the second part, or if it should also be a negative number.

any help would be appreciated!

2. Dec 5, 2007

### Staff: Mentor

The only thing that changes is the mass of the bullet. So figure her velocity in exactly the same way for both parts.

3. Dec 5, 2007

### pdubb

that works! thanks!