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Re: Pb



In the "short view" it seems the KE of the Pb changed from zero to something
(by gravity) then from something to zero (by the floor). These would seem
equal and opposite making work-floor equal minus work-gravity.

In the "long view," if we try to perform bookkeeping on the energy including
thermal energy, wouldn't we have to say some of the KE of the falling Pb
eventually ended up as thermal energy in the floor in addition to thermal
energy in the Pb? If we use the work-energy theorem to equate work with a
change in energy wouldn't we say the interaction between the Pb and the
floor resulted in less thermal energy in the Pb than there had been KE in
the Pb. If that is true would we say the floor did less work on the Pb than
gravity did on the lead; and the "missing energy" is in the floor as a
result of the work the Pb did on the floor?

If this is the thinking behind the original question, I can see why the
question was asked.

Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817