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Re: [Phys-l] A simple (?) question about speed



In response to my post, John Denker asked:

Is this a question about _speed_ ... or is it a question
about the meaning of _constant_ and its relationship to
_initial_ / _final_?

And John Barrer asked:

What was the rationale the students gave who chose "C"?

I don't have a list of their rationales. An informal poll of just a
couple students, as part of the classroom discussion, revealed that some
were thinking acceleration instead of speed, since we had been
discussing constant acceleration and what it meant to have a constant
acceleration vs. a non-constant acceleration.

Thus, I suspect they would have answered this correctly prior to being
introduced to acceleration but I don't know.

As for the meaning of initial and final, I believe students have
difficulty with that as well but they didn't mention that during the
discussion.

John Barrer also asked:

I
wonder if the answers would be different if the question were
reframed with a familiar context. "A car has an initial speed
of 30 mph and a final speed of 60 mph". Same thoughts
vis-a-vis the question posed later. Is the use of a vague
and/or context confounding the results?

That is an interesting question. If anyone tries it, I'd be interesting
to know what happens.

----------------------------------------------------------
Robert A. Cohen, Department of Physics, East Stroudsburg University
570.422.3428 rcohen@po-box.esu.edu http://www.esu.edu/~bbq