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Re: [Phys-l] momentum and energy





|
| 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.