# A circular body motion around its axis

1. Apr 26, 2009

### Mahmoud Ebied

Hello physicists
I have a circular body goes around its axis very fast.
I am seaching for answer for these questions
1- How can I calculate its momentum or the energy that it has?
2- What is the forces that limit its motion?

thanks a lot

2. Apr 26, 2009

### tiny-tim

Welcome to PF!

Hi Mahmoud! Welcome to PF!

You need to know the moment of inertia (I) of the body.

Then the angular momentum is Iω, and the energy is 1/2 Iω2, where ω is the angular velocity.

And the torque (moment of force) needed to produce an angular acceleration of α is Iα.