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Linear momentum conservation vs angular momentum conservation

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May15-11, 01:12 PM
P: 20
If linear momentum conservation is instantaneous in real time, then angular momentum conservation must be too. In other words, if you want to get something spinning, then you must physically turn something else in the opposite direction. Angular momentum conservation can't be implied, it has to have a physical, observable reality. Is this correct?
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May15-11, 01:48 PM
P: 33
Somewhat unclear, but that sounds good.


Are you trying to say that the conservation of linear momentum implies the conservation of angular momentum?

In that case, I could buy into that. It might be preferable to show this more rigorously by making arguments that rigid rotators are collections of point particles which obey linear momentum conservation.
May15-11, 03:17 PM
P: 20
We can use linear momentum conservation to induce angular momentum in another body through off center impact and subsequent adhesion. After impact, a non-rotating mass is moving in one direction, while a rotating mass is moving off in the other. Linear momentum is conserved, but in real time we have net angular momentum.

Angular momentum conservation is implied because of the misaligned centers of mass relative to the direction of travel, but remains a potential until the two centers are brought to a halt relative to each other. So how can angular momentum be the direct translation of linear momentum to rotating systems? There seems to be a qualitative difference here. It looks like total conservation remains a property of space until the 2 masses interact.

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