Re: oscillations test question

[John Barrer <forcejb@YAHOO.COM>]

It also neglects the fact that if the mass is hung so
that it is stationary at that stretch, energy has been
removed from the system (assuming that the mass
started at the elevation of the unstretched spring and
that they system is spring, mass,Earth). There's a
similar question in Serway where a mass is gently
lowered against a spring on a frictionless ramp. In
both cases, if the spring/mass combo are at rest,
energy had to be removed from the system. John Barrere
  Apex HS
--- "Carl E. Mungan" <mungan@USNA.EDU> wrote:
> 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.


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This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.