Chronology | Current Month | Current Thread | Current Date |
[Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |
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 {Mi(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.)