Re: [Phys-l] teaching energy

[Bernard Cleyet <bernardcleyet@redshift.com>]

My experience is belts permanently stretch, even tho. heating may reduce 
their length, and must be periodically tightened. Spring tensioning 
reduces this requirement.

bc

Brian Whatcott wrote:

> At 10:50 AM 9/29/2006, BC, you wrote:
>  
>
> > "The analogy to the rubber band is a visual example:  The band
> > changes its geometry as you stretch it, and energy resides in that altered
> > geometry.  Allowing the band to return to its "natural" geometry releases
> > the energy."
> >
> > Not a good example except in the "mind's eye"
> >
> > Try this experiment:
> >
> > W/ a high quality very large rubber band Stretch it and hold 'til
> > equilibrium.  Then using your lips as a thermometer (hold gently against one)
> > allow the band to relax.  If you are releasing it's energy it should warm,
> > right?  What does happen?
> >
> > Rubber makes rather interesting thermodynamic engines
> >    
>
> An aside:
> Fabric reinforced belts are used to transfer motion to water pump,
>  alternator, power steering pump etc.,  in the automobile.
> The curious property to which BC alludes, that these belts tend to
>  shrink when heated is unfortunate, in the context of the fixed
> tensioning methods formerly employed for cars.
>   So it is a very encouraging thing to see that current American
>  vehicles are adopting sprung tensioning pulleys.
>
>
>
> Brian Whatcott    Altus OK    Eureka! 
>
>
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