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Tom W wrote:
The words "A block slides along a table" are insufficient to
understand what the problem is.
What's unclear? Let me try again another way:
A block slides to rest along a level rough table. The only net force
on the block is kinetic friction. The table is clamped to the floor
and hence to the earth. We approximate the earth as being an inertial
system. The observer is at rest with respect to the table. I hope
this is clear. Now for the question:
HOW MUCH WORK DID THE BLOCK DO ON THE TABLE?
Since I only read the digest, I may as well provide a grading key
right now. If your answer was zero, congratulations, you are a
believer in pseudowork. If your answer was positive, you are
consistent in your use of thermodynamic work. A new text you may like
is Halliday, Resnick, and Krane 5th ed. (See the top left hand column
on page 283.)
Please do not alter the spirit of the question. You may *not* try to
put both the block and table in the system. The system is the table
(plus earth). You may *not* instead tell me about heat; my question
is only about the work. You may *not* answer by invoking a special
magical formula; the whole point of this question is to illuminate
how you think about work in general--the specifics of this example
are just there to give us something concrete to discuss.
Only three people that I know about are allowed to choose both
answers: they are John M, Joel R, and Gene M. John D has lots of
support here:
* all of the industrial researchers he polled - say 15 people
* all other active PHYS-L members interested in this thread - say 50 people
* the remainder of my dept - 35 faculty
So not only are industrial researchers unwilling to use pseudowork,
so are academic scholars. From this limited survey, we can say that
about 97% of all physicists are *hostile* to pseudowork. I chose the
highlighted word purposefully. As I have gone around my dept here at
the Academy for example, my colleagues tell me they not only don't
teach pseudowork, they believe it's a confusing, heretical term in
league with cold fusion, astrology, and such ilk. Here's a sample
quote of just this kind from the list:
Hey don't get me involved with a spurious thing called "pseudowork". I
disavow ever using the term out loud. There is enough nonsense in physics
teaching without introducing yet more.