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Re: conservation of momentum (was Re: Heat as an indestructible substance)



In response to your 3:

A) I do not consider cons of energy (1rst Law of Thermo) as a
generalization of any work-energy theorem of mechanics. The (pseudo) WE
theorem knows nothing of energy transfer or conservation. It merely
establishes the line integral of external forces over a system's CM path
as a numerical monitor of the system's KE increase. It says NOTHING about
where that energy came from - it would not even understand that question
or the concepts of energy sources and sinks. This is the expressed, and
exclusive, business of the FLT.

B) I think your wedding N3 to contact forces is ill-advised.
microscopically there are no such things - even the concept goes haywire
in my mind.

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor
----- Original Message -----
From: "Carl E. Mungan" <mungan@USNA.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Friday, May 09, 2003 11:14 AM
Subject: conservation of momentum (was Re: Heat as an indestructible
substance)


| . . .
| 3. I hope no one jumps on me for this, but I'll throw it out anyway.
| When it comes to energy, one has the pseudowork-energy (W-E) theorem
| which one can rigorously derive by spatially integrating N2. Then one
| has the broader conservation of energy law which includes W-E as a
| special case, but has been broadened beyond this by consideration of
| fields, internal energy, heat, etc. Could one choose to say the same
| about momentum: One can derive a "pseudoimpulse-momentum" theorem
| that applies to classical masses interacting by contact forces, but
| the broader conservation law also handles fields, waves, etc. . . .
|