Re: Controversial Exam Questions - Not Ohm's Law

[Jack Uretsky <jlu@HEP.ANL.GOV>]

        The same question, and Michael's correct answer, are in one of
Dick Hake's early SDI labs.  If anybody cares I can look up and see which
one.
                                Regards,
                                        Jack

Adam was by constitution and proclivity a scientist; I was the same, and
we loved to call ourselves by that great name...Our first memorable
scientific discovery was the law that water and like fluids run downhill,
not up.
                          Mark Twain, <Extract from Eve's Autobiography>

On Thu, 11 May 2000, Michael Edmiston wrote:

> 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.
>
> 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
>
>
> A woman is standing on a flat section of ground. Her weight is 500 N.
> Newton's
> third law states that there must be an equal and opposite force to her
> weight,
> which is
>
> A. the Earth exerting an upward force of 500 N on the woman.
>
> B. the woman exerting an upward force of 500 N on the Earth.
>
> C. the woman exerting a downward force of 500 N on the Earth.
>
> D. the Earth exerting a downward force of 500 N on the woman.