Re: [Phys-l] conservation versus constancy

["Bob LaMontagne" <rlamont@postoffice.providence.edu>]

John made the point I was trying to make better than I did.

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of John Denker
> Sent: Monday, October 16, 2006 2:51 PM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] conservation versus constancy
>
> There may not even *be* a valid far-field limit, especially if we are
> dealing with infinite-range interactions such as gravitation or
> electrostatics.
>
> =======================

Another example I would like to bring up about "elastic" is the following.
Take a cluster of identical steel balls held together by a number of
springs, such that the cluster is quite compact. Now let it slam head on
into an identical cluster from the opposite direction. The springs become
stretched and the balls oscillate in wild gyrations. The collision is over
well before the oscillations cease. In fact, if the springs and balls are
all "perfectly elastic" the random oscillations never cease.

Is this a perfectly elastic collision? That is, even given that all the
forces in the system are conservative (or "elastic"), is KE conserved? 

I bring this up because one of my students proposed something similar to
this.

Bob at PC