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I'm interested in hearing what folks think of the
following question
in the test bank for Giancoli:
Chap 14 #11. Two hundred grams hung on a spring
stretches it 8.4 cm.
How much energy is stored when stretched 8.4 cm?
Before reading the rest, decide how you would answer
this and why.
While a number of answers are possible, the most
reasonable answer in
my mind is zero. By definition, a system at rest in
stable
equilibrium is at a potential minimum.
The purported answer of 82 mJ only considers the
increase in the
elastic potential energy and neglects the decrease
in the
gravitational potential energy.
It is true that no zero points are specified. This
is why I can only
say my answer is reasonable, and other
interpretations are possible.
Comments?
--
Carl E. Mungan, Asst. Prof. of Physics 410-293-6680
(O) -3729 (F)
U.S. Naval Academy, Stop 9C, Annapolis, MD
21402-5026
mungan@usna.edu
http://physics.usna.edu/physics/faculty/mungan/
This posting is the position of the writer, not that
of SUNY-BSC, NAU or the AAPT.