# Moment of inertia of a disk

1. Nov 5, 2011

### deezy

1. The problem statement, all variables and given/known data
What is the moment of inertia of an 8 kg, 40 cm diameter disk for rotation through the edge of the disk?

2. Relevant equations
$$I = \frac{1}{2}MR^2$$

3. The attempt at a solution

Inertia at the center of the disk would be $$I = \frac{1}{2}MR^2$$, right? I'm not sure what the right equation for inertia at a point on the edge of a disk would be.

2. Nov 5, 2011

### Andrew Mason

Apply the parallel axis theorem to find the moment of inertia about a parallel axis a distance d from the centre of mass:

$$I = I_{cm} + Md^2$$

AM