Re: forces

["Dewey Dykstra, Jr." <dykstrad@varney.idbsu.edu>]

> In my (very naive) view, I would have agreed with John that students
> pre-understanding of 'force' is extraordinarily close to the physics
> understanding of it.  In what ways do you see a difference?
>
> Perhaps you are refering to the concept that force causes motion (rather
> than change-in-motion).  In that case I understand you, but I would label
> that as a pre-conception about the relationship between force and motion
> rather than a pre-conception about force itself.  I think that distinction
> may be important, although it may be a 'nit-pic'.
>
> --
> --James McLean
> jmclean@chem.ucsd.edu
> post doc
> UCSD

The difference that I am referring to *is* in the issue of what force is
seen to cause.  It is a conception nonetheless regardless of what prefix
you put on it.  If we change what we think something does, then what that
something is changes in some important respect, too.  This is not a nit-pic
because it is a major step for the students and one all too often missed as
a result of normal instruction.  It is not a nit-pic also because it is
central to the Newtonian notion of force and to the difference between the
Newtonian notion of force and previously existing ones; certainly ones the
students come to class with.

Regardless of the extent to which student notions of force might match in
statics (and there are significant ways in which even in statics their
notions do not match ours) it is still the case that this issue of the
relationship of force to motion is not addressed by attention to statics.

Your distinction is in fact important, because of the fact that it is about
the relationship of forces to motion.  Relationships between things are
intimately involved with the things themselves.  Hence, there needs to be
times in which the things are studied independently and when they need to
be studied in relation to each other.

Dewey

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Dewey I. Dykstra, Jr.                   Phone: (208)385-3105
Professor of Physics                    Dept:  (208)385-3775
Department of Physics/SN318             Fax: (208)385-4330
Boise State University                  dykstrad@varney.idbsu.edu
1910 University Drive                   Boise Highlanders
Boise, ID 83725-1570                       novice piper

"Physical concepts are the free creations of the human mind and
are not, however it may seem, uniquely determined by the external
world."--A. Einstein in The Evolution of Physics with L. Infeld,
1938

"Don't mistake your watermelon for the universe."  --K. Amdahl in
There Are No Electrons, 1991.
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