Re: Angular momentum definition
- From: "Dirk Van de moortel" <dirkvandemoortel@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 19 Jun 2007 19:03:30 GMT
"qwerty" <qwerty@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:Xns9954DAE871393p3ifw90nsdek@xxxxxxxxxxxxxxxx
I'm reading a book that defines angular momentum simply as
r x p (vectors)
taking r as the position vector from an arbitrary point of reference and p its momentum.
I thought we needed rotation to have angular momentum.
If you look at a sufficiently small portion of an object's
path, then every such part of any kind of motion can be
regarded as a "rotation" around any point, and every
such part has its own defining p-vector and its own
position vector w.r.t. the chosen point.
Defining angular momentum for rotation only (i.e. for
constant circular motion) would be much too restrictive.
The concept is useful through its conservation. It is not
only conserved when the object has constant circular
motion around a circle's centre. It is conserved around
any point, and that is what makes so interesting. If this
was not the case, no book would even bother to mention
angular momentum.
Dirk Vdm
.
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- Angular momentum definition
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