Oooops, an obvious typo!
SUM(Ri x Vi) should be: SUM {Mi(Ri x Vi)}
Bob Sciamanda
 Original Message 
From: "Bob Sciamanda" <trebor@WINBEAM.COM>
To: <PHYSL@LISTS.NAU.EDU>
Sent: Tuesday, March 15, 2005 1:54 PM
Subject: Re: conservation of angular momentum question
I would point out that the (mechanical) angular momentum of a system can
 always be written as an "orbital " plus a "spin" term. The spin term is
 truly a property of the system, since it is defined relative to the center
 of mass as "origin". Further, one need not use the CM for the origin of
 both positions (Ri) and velocities (Vi) in calculating
 L(spin) = L(cm) = SUM(Ri x Vi).

 In fact if one chooses one space point A for the origin of position
vectors
 and a second space point B for the origin of velocity vectors (ie the
origin
 for position vectors whose time derivatives are the velocity vectors),
one
 can show that the spin angular momentum is independent of the choices for
A
 and B, so long as one (or both) of them is chosen to be the system center
of
 mass. (IE, either the CM is the origin of the Ri and/or the Vi are
 calculated relative to the CM frame.)


 Bob Sciamanda
 Physics, Edinboro Univ of PA (Em)
 http://www.winbeam.com/~trebor/
 trebor@winbeam.com
  Original Message 
 From: "Leigh Palmer" <palmer@SFU.CA>
 To: <PHYSL@LISTS.NAU.EDU>
 Sent: Tuesday, March 15, 2005 11:34 AM
 Subject: Re: conservation of angular momentum question
 . . .
 Of course since angular momentum is a canonical quantity (i.e.
 calculated according to a conventional rule) it has no absolute meaning
 and thus no local meaning.

 Leigh

 * For an extreme example of multiple "recentering" of canonical
 angular momentum see Tad McGeer and Leigh Hunt Palmer, Wobbling,
 toppling, and forces of contact, AJP 57, 10891098 (1989).


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