# Question about Power formula

1. Nov 14, 2008

### shayrgob

The equation for power is:

F X 2pie X Revolutions

My question is, what is the 2pie for? I know that might seem obvious but I just can't see it.

thanks!

2. Nov 14, 2008

### Mentallic

I haven't seen the derivation of the formula, nor ever heard of it before. However, since there are 'revolutions' mentioned, the 2pi would imply that mathematically, the power is dependant somewhat upon circles. Given $$C=2\pi r$$

3. Nov 15, 2008

### shayrgob

I think I figured it out. 2pi = 6.28 radians, which is 1 complete revolution. So in the power formula you have Force X Displacement. To figure out displacement in a circle you take 2pi X the # of revolutions. I get it!!!

4. Nov 15, 2008

### Mentallic

Yep that sounds about right. Just be weary about your terminology though. I believe the correct term would be distance rather than displacement in this case.

5. Nov 15, 2008

### rcgldr

The equations for power are force times linear velocity, or torque times angular velocity.

The relationsips between angular and linear:

force = torque / radius
linear velocity = angular velocity x radius