Re: [Phys-l] "Unlearning"

["John Clement" <clement@hal-pc.org>]

> Re: Comment: "Why do HS teachers insist on teaching what must be
> unlearned?"
>
> You mean, why teach things we all KNOW are wrong, like F = ma or P = mv?
> Or why teach that thermal expansion is linear , or that air obeys the
> ideal gas law? Perhaps because in a wide range of important cases, it
> gives a useful working approximation that describes the world in which we
> live.

This is really a problem when physics is taught didactically.  But if the
students figure out the relationships using experiments and treat the
results as models, this should not be a problem.  After they have figured
out things, they should be asked to try to think of when the results might
be different.  In other words if physics is taught interactively with the
idea of models, this should not be as big a problem.

The difficulty is that most teachers act as sources of authority, and the
students are expected to learn the specific facts they were given.  The
textbooks are generally not much better.  There is an alternate approach
which has been shown in one case that I know of.  A historical treatment
where the various historical models are brought out and the students discuss
and debate their merits has been shown to work quite well.

And of course the books just treat the linear expansion with the same
authority as Newton's laws.  So students will think it is an absolute law,
rather than an empirical law.  So linear expansion is really a small topic
which can be omitted.

Most pre-college teachers have not been well exposed to the ideas of models,
so it is understandable that they do not treat physics as an exploration of
imperfect models that might be subject to change.  This is our fault for not
teaching at the college level in an interactive fashion.  They are just
mimicking the way they were taught in college.

John M. Clement
Houston, TX