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Re: The worm problem





On Fri, 28 Feb 1997 kowalskil@alpha.montclair.edu wrote:

I have no doubt that it was a challenging problem. The proof is that you,
and several others, found is worth working on. But I was left outside of
that "inner circle of smart guys". Let me exagerate and simulate a student
who is disapponted by the received grade. I am penalized for not guessing
what the professor had in mind. I am not stupid, I took him literally and
he gave me an F. That is not fair. Physics stinks. Why should I assume,
unless it is clearly stated, that the speed of the tractor is with respect
to the road while the speed of the worm is with respect of a constantly
expanding rope? Does the bug crowl as a worm (as a catapillar, as a flea)?
This was irrelevant to me; the length of the bug was not specified and I
assumed it was a point-like object. Therefore I did not try to deduce
the acceleration of the bug (with respect to the road) from the "mechanism
of walking". What was wrong with my reasonning? Why was I penalized? Who
said I was not thinking? Who said my mathematical sophistication is not
good? Who said ....?

You see my point. Problems should be formulated clearly. This is trivial
but here we are. Was I the only one who felt cheated?
Ludwik Kowalski


No you were not. I am also troubled by such ill-formed problems. But I've
heard arguments on the other side of this issue along these lines. Such
ambiguous and ill-formed problems are often the kind real physicists must
deal with in their work. They must infer reasonable assumptions, rule out
some possibilities as irrelevant, and finally, discuss and work out
several solutions (as was done here). This, it is argued, flushes out
those who thrive on such challenges and surmout them. I.e., the "ideal"
physics student we all seek, but seldom find.

This is fine if the results are in essay form, and evaluated by a
sensitive and knowledgable physicist who can recognize a correct and
insightful analysis even if he or she hadn't thought of it before and it
wasn't the answer anticipated. But if it is a multiple choice question, or
graded simply right or wrong, then it's clearly unfair.

But, examined in this light, many physics exams include such 'unfair'
questions.

I included one such on a recent Thermo exam: "One textbook says that the
first law of thermodynamics is 'essentially the law of conservation of
energy'. Another says that the first law says *more* than the energy
conservation law. Another says that energy conservation is a stronger
statement than the first law. Discuss." Actually, I included exact quotes
from the textbooks and named names. I didn't expect a right/wrong answer,
but a meaningful and insightful discussion which addressed the issues of
the definitions of work and internal energy in classical thermodynamics,
and the issue of quasi-equilibrium processes and path-dependent processes.
I'd have been overjoyed had anyone addressed the issue of what, exactly,
do the two laws say, and do they *include* the concepts of work and
internal energy, or are these defined separately? But when you look again
at the textbooks, these reasonable questions are often not addressed
forthrightly and clearly.

Crossing over to a parallel thread, I'll bet there are exams given in some
courses which actually ask students to name the classifications of levers!

-- Donald

......................................................................
Dr. Donald E. Simanek Office: 717-893-2079
Prof. of Physics Internet: dsimanek@eagle.lhup.edu
Lock Haven University, Lock Haven, PA. 17745 CIS: 73147,2166
Home page: http://www.lhup.edu/~dsimanek FAX: 717-893-2047
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