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Re: are normal reaction and tension conservative ?

At 08:46 6/30/01 -0700, John Mallinckrodt wrote:
On Sat, 30 Jun 2001, Chetan wrote:

are normal reaction and tension conservative ?

I think it depends on what forces are causing the normal reaction and
tension(like when two masses are hanging on the opposite sides of a pulley
then the tension in th rope is due to gravity which is a conservative force
and so the tension is conservative).

Is this right?

No, but this is a good question--the type only an uncommonly
thoughtful student would be likely even to think of.

... real ropes and real surfaces are generally at
least somewhat "dissipative." They exert forces that are not
completely calculable from their configurations and may exhibit
hysteresis and/or velocity-dependence. For instance, a rope may
(and usually does) exert a stronger pull at each specific length
while being extended than when it is subsequently allowed to
relax. As a result, the work done *by* an external agent to
extend the rope is smaller than the work done *on* the external
agent as it is allowed to relax.

John Mallinckrodt
Cal Poly Pomona

John's meaning though inadvertently reversed, was perfectly clear
from the context of the rope/work hysteretic example.
Moreover, I learned something about the idea of transferring a
conservation concept onto one of its constitutive components.
[There is even a word for this in literary and poetic contexts.]
Most important, I applaud his sympathetic treatment of the

brian whatcott <> Altus OK