Re: Stop using calories?

[LUDWIK KOWALSKI <kowalskil@alpha.montclair.edu>]

I am responding to Bob Scamanda (quoted at the end). 

Bob's teaser, and Timothy's message, can lead to interesting questions.

Suppose that a paddle experiment is performed under ideal conditions
(a gedanken experiment). There is no air above the liquid and walls are 
perfectly insulating. All solid substances are perfectly rigid and 
frictionless, even to the liquid. The constant V condition is satisfied. 
How can the constant P condition be satisfied without violating V=const?

You may say: this is impossible for water because it expands when the 
temperature is rising. A piston-wall must move to keep P=const thus
violeting the V=constant condition. I would say that a constant-P-and-V
process is possible, think about electrical Q-ing of water, near 4 C, in 
our perfectly rigid container. (Q-ing is a Martian word for heating). 
"ALL of the energy added" to a properly chosen liqiud does not have to 
"go outside", some of it may sometimes be used to make internal changes 
in the liquid.

Yes, Bob, I see the "ideal gas" wording in your message. This brings
another line of questions. The ideal gas will probably not be Q-ed at all. 
I suspect that it would offer no resistance to the accelrating paddles.
Is this correct? The presence of the gas will increase the moment of 
inertia of the the rotating system without contributing to  Q-ing. 
                                                        Ludwik Kowalski
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Bob Sciamanda (SCIAMANDA@EDINBORO.EDU) wrote:

> Steve wrote:
> > (b)  Our classroom holds about 6800 moles of air (molecular mass = 
> > 29.0 gm/mole). Suppose the temperature in the room is initially 20 C
> > and all the candy bar's energy is somehow delivered to the air
> > molecules. What will the final temperature be, and what will the rms 
> > speed of the molecules be?
 
> If you get more "realistic", the problem is even more fascinating.
> Under ideal gas, constant volume and constant pressure conditions, 
> ALL of the energy added to the air goes outside!
> I leave this as a teaser for those who have not seen it before. 
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