# Angular speed of bullet

1. Sep 6, 2009

### hitman38

Hey guys,

I have a bullet and its diameter is 0.5 inches. its speed is 400 foot /sec.
It makes one complete rotation in the gun 120 mm per turn and length of the gun is 1.5 meter.
How can I calculate the rotational and angular speed?

-I used a formula for rotational speed;
R=2pi.n n=(number of the rotation) which is 1.5 meter/1.2 mm.

- Angular speed;
w=v/r w=400 ftsec/0.5inch

Are my formulas and calculations correct?

2. Sep 6, 2009

### semc

Re: angular speed problem

wow 1.5 meter is quite a long gun haha. anyway if i am correct 120mm is the distance the bullet travel in one round correct? i would find out how many turns it need to make before it exits the barrel and use the speed that it is traveling. As for the diameter i have no idea what it is for

3. Sep 6, 2009

### hitman38

Re: angular speed problem

Yes u correct 120 mm is the distance the bullet travel in one correct.
I guess the amount of the turn is 1500/120=12.5
Given diameter may be for the angular velocity; w=v/r
But I am not sure about if i can use this diameter for angular velocity.

4. Sep 6, 2009

### kuruman

You are correct. The bullet does 12.5 revolutions inside the gun.

How many revolutions per second is that? Hint: you need to find how many seconds the bullet spends in the gun.
How many radians per second is that? That is your ω, the angular speed.