Re: Why work before energy in texts

[Roger Haar <haar@PHYSICS.ARIZONA.EDU>]

Hi,
        I guess I do not understand the logic of: "The
most fundamental should be introduced first."  If
so lets start with QED.

        It seems to me that for teaching usually it
should be: "The most familiar and simplest
first."   Early on one needs to build on the
students experience (including lecture and lab
experiences) and develop a vocabulary.  The term
"Energy" in popular use has many different
meanings, and when introduced in physics, the
introduction should be based on examples that
indicate the limited meaning used in physics.

        This is not to say I agree with some texts that
introduce energy so late, that energy conservation
is not used to describe elastic collisions.

Thanks
Roger

***********************************************************************
crawford j maccallum wrote:
> I truly believe and understand that energy is more fundamental than work &
> "should" be introduced first. But I still don't know how.  My beginning
> students know what force & displacement are, so they can understand work,
> and then I can show them that 1/2 mv*2 or 1/2 kx*2 or even mgh equals work
> done (I know, I know, I'm careful).  But if I start with energy why
> shouldn't it be mv*2 or mv*4, or why not mgh*2?  The only 'proper' way I
> know is to start with the expansion in power series of v/c of the
> time-like component of the covariant 4-vector ....!!?  Or Noether's
> theorem!!?
>
> Work is easily defined.  Energy is not .. it's just something that we can
> always find some way of accounting that makes it conserved.
>
> Help?
>
> Crawford