- #1

doktorwho

- 181

- 6

## Homework Statement

Determine the moment of inertia of a rigid body on the picture:

The radius of the inner cylinder is R and the outer is 2R.

## Homework Equations

3. The Attempt at a Solution [/B]

I thought of subtracting the big cylinder inertia from the small and adding the hanging body and i get:

##I=\frac{m}{2}(R^2 + 4R^2) + m(2R)^2##

but for some reason the book states its:

##I=\frac{m}{2}(R^2 + 4R^2) + \frac{m}{2}R^2##

Why is it like this? Isn't the body hanging from the the outher radius and is like a point mass?

Could you explain?

Last edited: