# Can the angular momentum of any rigid body (symmetrical or asymmetrical) be found this way?

Can the angular momentum of anybody regardless of whether its symmetrical about the center of mass or not be found by finding the angular momentum about its center of mass and summing it up with the angular momentum of the center of mass?

(Here the angular momentum of the center of mass would be the angular momentum from your reference point if you consider that all the mass of the body is placed at the center of mass. (retaining the same angular velocity) and the angular momentum about the center of mass would be the angular momentum of the body with the center of mass as the reference point.)

• A related College level answer physics.stackexchange.com/a/91246/392 – ja72 Nov 4 '14 at 14:20
• The best way to ask a homework problem is to ask the specific physics concept you're struggling with. The way you've phrased the question, you haven't quite done that yet, but it shouldn't be a tough fix. Just try to edit in a concept about the problem that is causing you to struggle. What makes this problem different/more challenging than other angular momentum problems you solve? – Sean Nov 4 '14 at 14:30
• Also note your level with familiarity with vector algebra (vectors, matrices, cross products and rotations). All are skills needed to handle problems like this in general. – ja72 Nov 4 '14 at 14:39
• Fixed now? I think its more challenging because the object is not symmetrical about the axis through its center of mass. – Hritik Narayan Nov 5 '14 at 13:37
• What is the "angular momentum of the center of mass"? Please clarify the two parts of angular momentum proposed, maybe with an expression or example. – ja72 Nov 6 '14 at 22:50

## 1 Answer

I hope that you are familiar with the calculus with vectors. Then you can find the answer in Wikipedia, "Angular momentum in classical mechanics", the entry "Angular momentum simplified using the center of mass". I had a look at it right now, it is very simple and clear. You will find that, no matter if the object is symmetrical or not, you can do the calculus as you supposed.

Good luck,

Sofia

• If you find difficult to understand the equalities Σm_i R_i = 0 and Σm_i V_i = 0, ask me. – Sofia Nov 13 '14 at 21:39
• So whatever I heard about symmetry affecting the way we find the angular momentum of a body must be wrong? – Hritik Narayan Nov 14 '14 at 12:33
• What exactly you heard? The calculus in Wikipedia is general. Please be more specific about what seems to you problematic, or, give an example. – Sofia Nov 16 '14 at 15:48
• Someone told me the way of figuring out the angular momentum for asymmetric bodies is very different from the method you gave^ (they didnt mention what method though) – Hritik Narayan Nov 17 '14 at 15:22