Re: Loss of KE

["John S. Denker" <jsd@MONMOUTH.COM>]

John Clement wrote:

1> The formalism that predicts the loss of KE is valuable because you can
> ignore the details of the collision, and just know whether the two objects
> stick together.

Yes.

2>   Physicists love to find conservation principles that ignore
>  the details of a collision because it makes problems easier.

Yes.

3>  However in the
>  process visualization of the microscopic details may be lost.

Yes.

4> This is unfortunate because it leads students to be equation hunters
> rather than problem solvers.

Huh?

Back in item #2 we agreed that solving the problem
was not just solved but more-easily solved by using
the conservation principle.  So how is a principle-user
not a problem-solver?

Calling them "equation-hunters" was evidently meant
to be disparaging.  Why?  And why not call them
principle-hunters?

Not everyone disparages principles.  Many people
consider the symmetries and grand conservation principles
to be the core and the quintessence of physics.

Would somebody here like to explain the "microscopic
details" of how energy is conserved during, say, the
metabolism of a fat molecule?  How about during a
nuclear reaction?

Are we going to disparage all of thermodynamics
because it makes a point of not discussing the
"microscopic details"?

> If you have a soft
> material such as clay it squishes gradually with a low force, over a long
> period of time.  If you have hard material such as quick acting glue, the
> squish is with a high force, very quickly.  In either case ....

Those cases do not exhaust the possibilities.  If
you are going to analyze details, it is particularly
amusing to consider two objects that "stick" to each
other by means of a hook-and-eye fastener or similar.
Imagine that the hook bounces off the walls of the eye
with a 99% elastic bounce.

These issues come up in real-world engineering
situations.  Recall the previous discussion of
rail-car couplings in general and draft gears
in particular:
  http://lists.nau.edu/cgi-bin/wa?S2=phys-l&q=draft+gears&s=&f=&a=&b=


While we're at it, would somebody like to explain
the "microscopic details" of why a piece of clay
is sticky as opposed to bouncy?  Just how does it
dissipate the energy, microscopically speaking?


This posting is the position of the writer, not that of 't Hooft,
Veltman, or Gell-Mann.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.