Re: CONSERVATION OF ENERGY

[Bob Sciamanda <Sciamanda@worldnet.att.net>]

LUDWIK KOWALSKI wrote:
> You are correct, Bob, for a single particle MODEL. But the reality of the
> situation is more complicated. Two internal non-conservative forces are
> involved in a process by which internal kinetic energy K (macroscopic)
> is converted into thermal energy (microscopic). And if my understanding
> of Bruce Sherwood is correct (his AJP article was mentioned here) it is
> not at all obvious what fraction of the really-observed x should be used
> to calculate the work correctly. 
>                                     Ludwik Kowalski

I should simply reply "I rest my case" with regard to my previous 
contentions that muddying the meaning(s) of the word "work" (as a 
result of confounding the Work Energy Th.(WET) with the First Law of 
Thermodynamics(FLT) ) yields only confusion.

The meaning of the word "work" in the WET is very clear (I have 
previously made it explicit).  The FLT states that a defined system 
has a state function (we name it the internal energy E) which is a 
numerical quantity with units of Joules (like the terms in the WET). 
The FLT further states that the numerical value of E can change by 
a variety of kinds of interactions with the system's surroundings;  
one way which is almost always available is by an exchange of "heat", 
dQ, across a temperature gradient. Other ways will be peculiar to the 
situation and may involve electrical, magnetic, etc interactions.

The FLT simply leaves a space for the appropriate terms within 
the ill-chosen symbol dW (Exactly as Newton left a space for 
appropriate forces in the left hand side of F=ma).  Our mathematical 
models of dW find it useful to express it as dW = Y*dx, 
an intensive variable times the variation of an extensive variable. 
Each interaction will thus be modeled by an appropriate term, which will 
have units of Joules.  

Only in some few carefully contrived situations will this interaction 
term be identical (conceptually or numerically) with "work" as used in 
speaking of the left hand side of the WET. In the FLT dW is "whatever 
it takes" to keep the conservation of energy books straight;  this is 
not an explicit concern of the WET; it is simply  a corallary of 
Newton's "laws of motion". 
-- 
Bob Sciamanda		sciamanda@edinboro.edu
Dept of Physics		sciamanda@worldnet.att.net
Edinboro Univ of PA	http://www.edinboro.edu/~sciamanda/home.html
Edinboro, PA		(814)838-7185