Re: The worm problem

["Donald E. Simanek" <dsimanek@eagle.lhup.edu>]

On Sat, 1 Mar 1997, Richard E. Grandy wrote:

> > Ludwik and Donald objected to my statement of the rubber worm problem as
> > being ill formed. I went over Ludwik's complaints, but I easily recognized
> > that he was being ironic. Donald, however, makes me wonder. The problem I
> > posed is included below. I would appreciate a serious comment on just how
> > this problem is ill formed.

Perhaps I read it hastily. I may have been thinking of the continuous case
and wondering how the finite length of the worm might affect matters and
whether the worm was also stretching as it walked, and would that matter.
I was also wondering if it was a many-legged worm, like a millipede, how
many legs it had, what was the length of its pace, the period of each step
and what was the pattern of leg motion, front to back or back to front. I
also wondered how you'd train a worm to march in a straight line along the
rope. On reading the problem again, I must agree that it is completely
specified. It is, however, artificial and unrealistic as a physics
problem. It is a nice mathematics problem. 

What I was really complaining about in my post was the kind of problem one
often sees in physics books in which an artificial situation is presented
using words and images which imply a real-world setting. These often throw
students off the scent, forcing them to strip away these embelishments to
get at the heart of the matter. The best students will do this, and thrive
on it. The rest will be confused and frustrated, and complain that
physicists must live in some wonderful ivory tower where worms crawl in
straight lines, pulleys are frictionless and massless, projectiles travel
in parabolic paths, and V = IR where R is constant. 

	-- Donald