Re: Controversial Exam Questions - Not Ohm's Law

[Rick Tarara <rbtarara@SPRYNET.COM>]

Before we reopen the 'what is weight' debate--I suspect Mark to be in the
'what the scale measures' camp and not the 'gravitational force due to the
earth' camp--let me just comment that the exam question points to the
problem of 'going one's own way' on these issues.  Certainly students taught
that weight is what the scale reads (you really are weightless in orbit)
will be at a disadvantage on this question (although there is no other
'better' choice than B, even from this viewpoint).  The 'standard
curriculum' is pretty much set by the consensus found in the popular texts.
While individual texts certainly have errors, the disagreement (often seen
on this list) with certain common approaches and/or 'facts' found in these
texts usually fall into the 'well that's a different interpretation'
category.  The interpretation is not necessarily wrong (and neither is the
text-book approach) but if one's students are expected to take
'standardized' tests, one should be wary about teaching 'outside' the
mainstream curriculum.

That having been said, I'm sure people will want to argue strongly that
their way is correct, the common wisdom of the textbooks is wrong, and
obviously we need to teach what is RIGHT!

Rick

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Richard W. Tarara
Associate Professor of Physics
Department of Chemistry & Physics
Saint Mary's College
Notre Dame, IN 46556
219-284-4664
rtarara@saintmarys.edu

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----- Original Message -----
From: "Michael Edmiston" <edmiston@BLUFFTON.EDU>

> I think the question and answer are correct.  If the woman's weight is the
> gravitational force the earth exerts on her, then the reaction force is
the
> gravitational force she exerts on the earth.  Answer B is correct.
>
> The problem is that many students will view her weight as the contact
force
> her feet exert on the earth.  The third-law reaction to the contact force
of
> her feet on earth would be answer A.  In order to make answer A correct,
the
> problem would have to be reworded to replace "opposite force to her
weight"
> with the words "opposite force to the force she exerts on the ground."
>
> I believe weight is defined as the gravitational force the earth exerts on
a
> body, and if that is true, the question is okay and B is the correct
answer.
> Now, the question is this... is that what the exam writers wanted to find
> out?  Were they trying to see if the students could make this distinction?
> It appears to me thy might indeed be after exactly that.