Re: [Phys-l] teaching energy

["Bob LaMontagne" <rlamont@postoffice.providence.edu>]

OK - given: 

> A) In the classroom:
>   Book on high shelf = high potential energy.
>   Book on lower shelf = lower potential energy.

How does height become magically transformed to motion? Height and motion
are entirely different entities. It's actually the gravitational force
producing the change in KE. PE only provides a convenient calculational tool
that allows the student to easily compute the change in KE when the
elevation of the object changes and gravity is the only force involved. To
me, that is the essence of energy - a scalar calculational tool that acts as
a very convenient surrogate for Newton's 2nd Law. I find it ill conceived to
encourage a student to somehow turn potential energy into some kind of a
substance that can (with the proper incantations) magically appear as KE.

Energy conservation can be presented as simply an equation that solves
motion problems in a path independent form. The mental image of something
transforming to something else is extraneous and prone to a mystical
interpretation of physics. I'm not advocating eliminating teaching energy -
just don't reify it.

I'll shut up at this point because I realize this topic has been talked to
death in the past and is probably boring the socks off most readers

Bob at PC


.
> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of John Denker
> Sent: Saturday, September 30, 2006 8:05 PM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] teaching energy
>
> On 09/30/2006 05:44 PM, Bob LaMontagne wrote:
>
> > Potential energies, on the other hand, are way of easily calculating how
> a
> > conservative force will change a KE if an object changes position. That
> is
> > difficult, if not impossible, for a student to associate with a concrete
> > image.
>
> A) In the classroom:
>   Book on high shelf = high potential energy.
>   Book on lower shelf = lower potential energy.
>
> B) Student pilots have an _easier_ time estimating their height (PE)
> than their airspeed (KE).
>
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