Re: first law of thermodynamics

[Jim Green <JMGreen@SISNA.COM>]

> More likely we are getting tangled up in the
> definition of "equilibrium".
>
> Here's a simple example.  (I regret previous
> unnecessarily-complicated examples.)  How about
> a simple pendulum, or a mass on a spring.  It
> converts energy from PE to KE and back, largely
> reversibly, but it's nowhere near equilibrium,
> according to the most-common definition of
> equilibrium.

Ah, but John, there wouldn't be a tangle either way if the two of you would
not treat "energy' as a "substance-like fluid".  The level of energy can be
changed by doing work but if it is pictured as "moving" the picture gets
muddied.

This caution is amplified by treating PE the same as KE -- even if one
pictures energy as a property as one should.  PE is not a property called
"energy"; it is the "potential to change the energy level" by doing
work.  KE is not "converted" to PE in the sense of a fluid.  PE is work.

Now we are to a semantics issue: But this is where concepts are
examined.  If we all agreed on the terminology and held the correct physics
in our heads while we converse, we would be OK.  But we don't.  First the
terminology gets skewed and then the physics.

As in the current thread.


Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen