Re: energy change

[Jim Green <JMGreen@SISNA.COM>]

> > In a collision, the ball transfers energy into the wall on the
> > "way in" and recovers it (all of it if perfectly elastic) on
> > the "way out".
>
> If you enter a mall holding a hundred dollar bill in your hand,
> stick it in your pocket for security while window shopping, and
> then remove it again when you leave, would you say that you had
> transferred money to and from the mall?

I say again:  "energy" of a system can be increased  or decreased  by doing
work, but it is not a substance  which can be "transferred".  John is quite
helpful here but he still seems to picture energy as a substance -- in this
case a dollar bill.  One  uses this picture at  his own peril.  And the
discussion becomes foggy as has been demonstrated again in this thread.

The language of physics should retain precision  --  so as not  to muddy
the water -- I mean  fog the air.

One might say -- with somewhat less peril -- that a deposit can be made at
one's local bank and dollars withdrawn from a distant bank.  No paper
dollars move.  Not perfect, but I think a bit better.

I will now  return to my little corner of the galaxy.

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