Re: Energy as ability to do work

[Joel Rauber <Joel_Rauber@SDSTATE.EDU>]

> > John, to expand the discussion; I'd agree with your point
> above; however,
> > would you consider it wrong to view the center-of-mass
> kinetic energy of a
> > rigid extensive object as being its ability to do work?
>
> Joel & John -- yes there is always the work/energy theorem which would
> agree with Joel, but I think that the advertised phrase is
> not helpful.

Jim, I tend to agree that the advertised phrase is not helpful; and rarely
if ever mention those words in my classes.

> First, as John points out, it is not always correct.

And I certainly follow what John pointed at as cases where it isn't correct.
I guess I was mostly wondering if there were cases that we might agree the
phrase-ology is correct, *even* if not helpful.

> And, the cart is before the horse - so to speak -- it is "work" which
> changes the "energy" not the reverse.  One would not say that
> acceleration
> is the ability to produce force would one?  Work is the
> "cause" and change
> in energy is the "result".

This is the way I usually view these matters.

Joel

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