- If the object is just a few compact chunks of mass, use
- If the object is extended, with a non-uniform density,
you'll need to break the object into simple little pieces
and add up the moment of inertia from each piece:
- If the object is a simple geometrical shape, AND it has a constant density, AND it is rotating around its center, you can look it up in a table of common shapes; any textbook will have such a table, or you could use this table of moments of inertia (PDF) or this copy of the table in PNG format.
- If the object is a simple geometrical shape,
AND it has a constant density,
but it is NOT rotating around its center,
you can use the table in your textbook
and the
**parallel axis theorem**. Read Section 9.5 or this very brief explanation .

Copyright © Michael Richmond. This work is licensed under a Creative Commons License.