# Moment of Inertia of a thin circular disc

*From*: qwerty <qwerty@xxxxxxxxxxxxxxxxxxxxxxxxx>*Date*: Tue, 19 Jun 2007 22:27:08 +0000 (UTC)

The disc has uniform density. The mass of a slice (like a pizza)

of the disc is:

dm = (M/2pi) * dtheta

theta: the angle of the slice in radians

M: the mass of the disc

So to find the moment of inertia:

I = (Integral from 0 to 2pi)R^2 dm = M*R^2

That's incorrect, as the moment of inertia of a circular disc is

M*R^2/2.

So what am I doing wrong?

.

**Follow-Ups**:**Re: Moment of Inertia of a thin circular disc***From:*PD

**Re: Moment of Inertia of a thin circular disc***From:*Ben Rudiak-Gould

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