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Re: [Phys-l] non-conservative --> non-grady ???



I think I am confused here for the same reasons. My understanding is
that the game here is to demonstrate that a conservative force can
increase the TOTAL energy of a system (not just simply do work). I am
having a hard time seeing how the example presented can be an isolated
system.

Bob at PC

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of Steve Highland
Sent: Wednesday, February 20, 2008 10:31 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] non-conservative --> non-grady ???

Your capacitor example would work the same even if you left the field
on
for
the entire time since the electric field outside the capacitor is
zero.

I'm not quite sure what the issue is that you are trying to address.
Has
someone claimed that conservative forces cannot do work? Of course
they
can. Gravity pulling a falling ball downward does work on the ball.
If
you
define the ball alone to be your system, then its energy increases as
it
falls. The ball by itself isn't a conservative system.