# Moment of inertia help

1. Nov 27, 2011

### mcsnowmo

Moment of inertia help!!

I have a question about moment of inertia. How do you calculate an object that is away from the axis of rotation? Im trying to figure out how to find the total angular momentum of two disks. One disk is rotating around the origin. Disk 2 is connected to disk 1 and is a distance L away and rotating at a different angular velocity. Im trying to figure out if i need to use the parallel axis theorem for disk 2 and if i can sum the two disk's angular momentum's to get the total momentum. I also need to find the total kinetic energy. any help would me much appreciated. thanks.

2. Nov 27, 2011

### JHamm

Re: Moment of inertia help!!

Angular momentum is calculated in two parts; first you take the cross product of the center of mass of your object with it's velocity relative to your reference point, then you find the spin angular momentum of that object which is the angular momentum it gets from spinning about its center of mass and is calculated as $I \omega$. Just add these two together to find the total angular momentum about some point :)