Re: plug and chug

[John Mallinckrodt <ajm@CSUPOMONA.EDU>]

> 1. The same skier comes off the hill and stops on a level spot.  Her
> friend pushes the skier forward with a force of 15.0 N. Find the
> skier's acceleration. (The coefficient of friction was given as
> .0500, the skier's mass as 75.0 kg).

<NITPICK> I think we may have discussed this one before.  My best
answer would be that the problem is ill-posed.  Assuming that the
skier is initially at rest (which the problem seems to be clear
about), then her friend may "push on the skier's back" with a force
of 15 N but her friend can't "push the skier forward" with a force
that small.</NITPICK>

Of course, it does depend on how you interpret the words but I think
most people would interpret the words as implying that the skier
*does* move forward.  I don't mind "tricky" questions in general, but
trickiness shouldn't depend upon the purposeful choice of misleading
words and I suspect that the class results could be significantly
different if the words "the skier forward" were replaced with "on the
skier's back."

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