# Comparing rotating bodies

1. Aug 29, 2004

### Gmaximus

If there are two rigid bodies rotating, (known I) how can you compare their rotation?

Example:

If the object of moment of inertia I is spining at x rad/sec, and its I is changed to i, what is the new speed?

2. Aug 29, 2004

### Staff: Mentor

Assuming that no external torque has been introduced, angular momentum will be conserved. So $I_1 \omega_1 = I_2 \omega_2$.