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Re: SR examination question



I think John Mallinckrodt is correct that a reasonable allowance for
assumptions still results in a problem with two answers, and it is not clear
what the exam author intended.

On the other hand, depending upon the level of student this exam was written
for, perhaps John's double answer is exactly what was intended. A question
I often ask after we study magnetism has a very clear answer in my mind even
though some students view it as a trick question. I draw a picture of
brushes and commutator connected to an armature in the field of a permanent
magnet. The question is: Is this a picture of a motor or a picture of a
generator? Even though the book, my lectures, and my demonstrations all
have shown this could be either, perhaps a fourth of the students will swear
it is a motor, another fourth will swear it is a generator, and half will
give the intended answer that it could be a generator or motor depending on
how it is used.

I think this type of question is valuable to see which students really
understand the situation, and I don't view this as a "trick question,"
especially once the students become aware that I sometimes ask this type of
question.

I have no idea whether the writer of this relativity question had that in
mind or not, but I don't think we can rule it out.


Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817