# Homework Help: Moment of Inertia lab equation

1. May 2, 2012

### fisselt

I'm working on a lab where I have to go into some detail about moment of inertia. I understand the concept and everything but am a little confused by the equation that I found on wikipedia.
I've seen only two equations for this: momentum=torque divided by angular acceleration and
one specifically for a disk: I=.5MR2

On wikipedia I they have the equation: T=ml2$\omega$2
Wikipedia makes sense to me because I understand that as radius decreases momentum decreases at constant angular velocity. Neutron stars for instance maintain similar inertia at reduced radius but much higher angular velocity.

Are all 3 ways true?

2. May 4, 2012

### Screwdriver

I'm assuming you meant that moment of inertia = torque divided by angular acceleration, because what you have there isn't true (just look at the units.)

I agree with this.

I'm assuming that you're referring to this page. You'll note that $T$ is in fact the kinetic energy of the object and not the moment of inertia. You may have been confused just because $T$ is similar to the symbol for torque, $\tau$.