> What I am saying is that if distance=0 then force could
> be infinite, but no work is needed.  i.e., given a strong
> enough support, you can hold up any amount of mass
> without performing any work.

And without consuming any energy.

Or, to put it another way, when was the last time the
batteries ran out on your chair and it collapsed under you?

When I was younger, I used to think floating cities (i.e.,
Cloud City in "The Empire Strikes Back") were an
impossibility because of the massive amount of energy
needed to hold them up.  Then one day I realized that if
the losses in the system were small enough (high Q),
you could run the thing for decades on a watch battery,
as long as you don't plan on raising or lowering it.

Because mechanical energy is force integrated over
distance, if one or the other of those components is
zero, the net energy change is zero, too.

Mike H.
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