"George Dishman" wrote in message ...
"Jim Greenfield" wrote in message
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(George G. Dishman) wrote in message
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(Jim Greenfield) wrote in message
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I then
suggested that a piece of rock subject to this type of experiment in a
valley should give a different result from an identical piece at the
mountain top-- silence........

Erm, well, yes, I can undertsand that. How do you propose
to store the energy? Is it a springy piece of rock? Why
would it matter where you do the experiment?

The rock is held up by the mountain. I just wonder does the higher
rock have more mass due to its altitude (and increased gravitational
potential energy)

No, AFAIK the rock has the same mass as if it was lower
and so does the planet. The mass of the system is probably
the same because raising the rock from the bottom needed
energy. Put the other way round, if you throw the rock
of the mountain into a pool. there is a loss of potential
energy that is converted first into kinetic as the rock
gains speed while falling, then into heat as it is slowed
in the water. Total energy remains constant so total mass
also remains constant.

Compessing the spring required (work) energy input as well. If gravity
is used to perform the compression, a larger piece of rock is needed
at the top of the mountain than in the valley, as gravity is less at
the higher level. But the same amount of energy (mass) is stored in
the spring (if the calorific thing is correct). I think this shows
that potential (gravitational) energy SHOULD contribute mass to the
higher rock, and R&B's individual masses would be greater at distance
due to the increased potential (for gravity to accellerate them)

Yes, that is the key, but perhaps you missed the earlier posts.
The question is how does the mass of the system compare to the
sum of the masses of the individuals in two different scenarios:

1) R&B are relatively far apart so gravitational effects are
negligible. They are rotating about a common point at high
speed tethered by a (massless) rope. Jeff and I agree the
mass of the system must be _greater_ than the sum of the
masses of R&B because the kinetic energy of their motion
must be included.

The "massless" rope is tensioned, as is a compressed spring. Otherwise
R&B would fly apart.

I was assuming the rope did not stretch. Energy is force
times distance (the integral if the force varies) so if
the rope doesn't stretch there is no energy stored.

Don't you mean "work is force times distance"- tension in the rope is
equivalent to tension in the spring, is to tension in the mountain
supporting the rock

,......and think about bringing opposing magnetic poles close- work is
done, but if I lock them in proximity, and then do the "calorific mass
equivalence test", will I see an increase in the mass of the magnets?)

Jim G