Physics puzzler was Flat Facts

[David Nereson]

Alan wrote:

>Andre's post still leaves the question unanwered, for me. For the system to
>wind down like that, the tension still has to go somewhere, i.e., if the
>string relaxes, something else is tensing up, so to speak.
>  
>

    No, when they first strung the piano, they altered the at-rest state 
of the string(s) by pulling up the tension.  When it goes flat, it's 
just responding to its natural tendency to return to the at-rest state 
of its molecular structure.  The energy was expended by the piano 
stringer.  Its going flat is the equal and opposite reaction to the act 
of pulling it up to pitch. 

>Reminded me of this question that my old high school physics teacher posed:
>"I you wind a watch spring extremely tightly into itself, then put it in a
>stainless steel case that fits snug enough so the spring cannot unwind, then
>add a drop of water and acid, then seal the whole system shut so no moisture
>can enter or leave, the spring will eventually dissolve/rust away. Where did
>the energy of coiled spring go?"
>
>This may even relate to our piano question. I'll post the answer later.
>This, BTW, was an experiment actually performed at some university or other.
>
>Alan R. Barnard
>Salem, MO
>
>The spring didn't have any energy.  Energy was expended by the person who wound it up.
>  
>
    --David Nereson, RPT