Re: [Phys-l] basic laws of motion +- vectors +- angular momentum

[Jack Uretsky <jlu@hep.anl.gov>]

	I fail to see how this rather arbit rary definition leads you to 
anything useful regarding, say, a two particle system.
					Regards,
						Jack




On Tue, 9 Dec 2008, Dan Crowe wrote:

> In nonrelativistic classical mechanics, the angular momentum of a single particle is r x p, where r is the vector position of the particle relative to the origin of a coordinate system, p is the vector linear momentum of the particle in that coordinate system, and the coordinate system is at rest in an inertial frame of reference.
>
> Daniel Crowe
> Loudoun County Public Schools
> Academy of Science
> dan.crowe@loudoun.k12.va.us
>
> > > > Jack Uretsky <jlu@hep.anl.gov> 12/9/2008 3:18 PM >>>
> Hi all-
> We probably all struggle with this from time-to-time, lured on by
> the similarity of language.  Linear momentum, angular momentum; both
> involve momentum, no?  So both should be conserved for the same reason, no?
> And the answer is, no.
> We can apply Newton's laws 1&2 to a single particle in an inertial
> frame, and already we get conservation of momentum.  For a single particle
> in an inertial frame, however, angular momentum has no meaning.  So in order
> to discuss angular momentum, we must begin considering systems of
> particles, and we are entering a whole new scenario, requiring a brand new
> language.
>
> Regards,
> Jack
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