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Re: [Phys-l] momentum and energy



Its not a matter of memorization for me either. Its more a matter of
fighting the tendency to think that appropriately knowing subject means
having a gazillion formulas at your disposal to simply plug into,
without thinking. I've oscillated back and forth over the years
regarding whether or not to provide an equation sheet (my current
meta-stable state) or letting my students write their own sheet. There
are pros and cons, as with much in life, with either choice.

________________________
Joel Rauber
Department of Physics - SDSU

Joel.Rauber@sdstate.edu
605-688-4293



| -----Original Message-----
| From: phys-l-bounces@carnot.physics.buffalo.edu
| [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf
| Of Richard Tarara
| Sent: Monday, November 13, 2006 4:55 PM
| To: Forum for Physics Educators
| Subject: Re: [Phys-l] momentum and energy
|
| It's not a question of memorization for me. I allow them a
| piece of paper (one piece for the semester) that they can
| write equations on, but they are admonished NOT to include
| solved problems or equations that pertain to very special
| cases (of which the below are examples--not totally derived
| in their text either). However, since I did not specifically
| remind them of that rule, I could only take a couple points
| off--but my collision problem between an alpha and an Oxygen
| nucleus was no challenge for anyone with the equations.
| Actually I was trying to see if I could trip them up in that
| the previous year's test had a collision between a proton and
| an alpha. ;-)
|
| Rick
|
|
| > [Original Message]
| >
| >
| > |
| > | Pull these equations out of a textbook (my students did for their
| > | last test--despite instructions not to do that kind of thing):
| > |
| > | Elastic collision with M2 initially at rest
| > |
| > | V1F = (M1-M2)V10/(M1+M2)
| > | V2F = 2M1V10/(M1+M2)
| > |
| >
| >
| > Amusingly enough, though not surprising, I have the same issues.
| > Therefore on my last test about ten days ago one of the
| problems was:
| >
| > Derive the V1F equation above.
| >
| > (I gave the equation to be derived, so those who had memorized the
| > equation had no advantage.)
| >
| > Those that merely memorized that equation . . .
| >
| > In a similar vein, I often ask range problems, where the
| "range formula"
| > won't yield the correct answer.
| >
| > Its rather difficult to fight the rote memorization monster; but
| > asking some questions where starting with basic principles
| yields the
| > correct result and using some memorized expressions don't
| is one way.
|
|
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