Re: Car acceleration

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

At 8:55 -0400 2/2/02, Chris Horton wrote:
> One could argue that E is the correct answer: The force of the foot on the
> pedal causes a chain of events with the result that the car accelerates.
>
> No, I am not just being facetious.  The joker in this deck is the word
> "causes".  This word as commonly used (and I don't remember it being
> redefined in any physics curriculum) does not preclude any number of
> intermediate agencies, time delays, etc.
>
> A better wording might be "What force acts on the car to accelerate it
> forward?"

The upshot of this discussion, it seems to me, is that the question
is a very poorly worded one, and one can make plausible arguments for
several of the choices, although it is clear to me that the intended
answer was the friction force. In a multiple choice question, where,
presumably, the student has only a minute or so to decide on an
answer, the distractors need to be either incorrect by direct
observation, or derivable from incorrect principles. This is not the
case here.

There is a conservation of labor law operating here, I think. In a
free-response question, the time to grade it is large, but the time
to prepare it is relatively short. Multiple choice questions, on the
other hand are graded quickly, but it takes a long time to prepare
good, unambiguous questions that measure what you want to measure.
Either you pay now or you pay later.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

(919) 467-7610

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