# Bullets Bouncing off Superman

1. Feb 20, 2006

### Swagger

It is well known that bullets fired at Superman simply bounce off his chest. Suppose that a gangster sprays Superman's chest with bullets of mass m = 1.8 g at a rate of R = 200 bullets/min. The speed of each bullet is v = 460 m/s. Suppose the bullets rebound with no change in speed. What is the average force exerted by the stream of bullets on Superman's chest?

THANK YOU!

2. Feb 20, 2006

### Galileo

Use Newton's 2nd and 3rd laws. Force equals the rate of change of momentum.

3. Feb 20, 2006

### Swagger

Well I have tried using Impulse (change in p = F * time) and I am not getting it right. The change in momentum is 1.656, right? And then you should be able to just plug in...using 60 sec for time, right?

4. Feb 20, 2006

### Galileo

Correct, 1.7 kgm/s is the change in momentum of one bullet. Now just calculate how many bullets hit per second for the total change in momentum per second.

5. Feb 20, 2006

### Swagger

I got it! Thanks!