Re: energy introduced without work

[Joseph Bellina <jbellina@SAINTMARYS.EDU>]

On Thu, 11 Oct 2001, John S. Denker wrote:

> Energy is a tremendously useful concept.  For example, it allows you
> to calculate the height-versus-speed tradeoff in a roller-coaster or a
> swing-set quite easily.  You don't need to talk about vectors or
> forces or work.  All you need is conservation of energy, plus the
> assumption that KE and GPE are dominant, in the sense that very little
> energy is converted to forms other than these two.
>
> .... You get the idea.  Energy is fundamental and primary.
>
> There is something quite sweeping and quite grand about this.  The
> height-versus-speed result is INDEPENDENT OF MECHANISM.  I don't care
> what mechanism is used to convert GPE into KE.  The roller-coaster
> uses one mechanism, and the swing-set uses another.  But the result is
> the same, independent of mechanism.
>
> To me, this is what physics is all about.  This is the magic and
> beauty of physics.  Engineering is all about mechanism, but physics
> can make grand sweeping statements that transcend mechanism.
That is an interesting point of view...the mechanism in not essential, but
energy is.  I agree there is value in being able to determine something
independent of the mechanism, since you can procede without having the
mechanism.  Thermodynamics is a wonderful example of that.  But it seems
to me to be sterile in a way...I think we want mechanism...not for the
engineering reason, but because physics is the study of causes...and that
requires more than accounting and limits on possiblities..which is what
energy considerations give you...it requires a detail belief about how
things happen...how it is that objects in the world relate to each other.

Thats how it seems to me.

joe

Joseph J. Bellina,Jr.               219-284-4662
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556