# Moment of Inertia

revres75

## Homework Statement

This was an exam question that I got wrong, my teacher tried to explain it but it only left me more confused. I found some websites that also had explanations but they were also confusing.

"Derive the moment of inertia of a uniform disk which rotates along a central axis , radius R , disk thickness d, mass M , density p
I= R^2 dm"

I= 1/2*M*R^2 ?

## The Attempt at a Solution

mass M = Pi*R^2*d*p

My teacher mentioned something about a third integral.

## The Attempt at a Solution

Presumeably you are to derive the moment of inertia by evaluating $\int r^2 dm$. So what did you do?
If I derive $\int r^2 dm$ I get 2r but I not sure what to do with the dm
If I derive $\int r^2 dm$ I get 2r but I not sure what to do with the dm