# Bullet passing through two holes

1. May 30, 2009

### physics10189

1. The problem statement, all variables and given/known data
so this is a classic problem...if you know what i mean.

The speed of a moving bullet can be determined by allowing the bullet to pass through two rotating paper disks mounted a distance .082m apart on the sam axle. from the angular displacement 24.9 degree of the two bullet holes in the disks and the rotational speed 819rev/min of the disks.
What is the speed of the bullet. in m/s^2

2. Relevant equations

3. The attempt at a solution
I try to find time from the starting point of the bullet till the second hole

time=(distance*2pi)/(full revolution of the disk*the degree)
then use that time and put it in the equation of
x final= velocity initial*time.

but didnt get it so any suggestion?

2. May 30, 2009

### tjr39

First you should change the rotational speed into usefull units ie radians or degrees per second

Second, you need to use the angular displacement and the rotational speed to find the time it took for the bullet to pass from first to second piece of paper.

Third you will need to use this time and then the distance between the bits of paper to calculate the speed of the bullet. Done!