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Re: acceleration



On Sunday, November 23, 2003, at 06:31 PM, Leigh Palmer wrote:

Bob Sciamanda wrote, as a PS to an example he surely did not mean to be
used for instructional purposes:

... there is nothing inherently special about the turnaround point in
a free fall vertical toss as observed from the ground. Go to the
inertial frame of a vertically moving helicopter and you can make any
event in the ball's travel the turnaround point (or eliminate the
turning point altogether).

Bob has here made the important point in the clearest, best possible
manner; it should not be relegated to PS status. If students can be
made to appreciate this point early in their "introductory" course,
when it comes time to introduce so-called frame forces later, and, of
course, the principle of equivalence.

The introductory physics course is misnamed since it is not a first
course. Students in this course come from diverse high school physics
courses. I have often been told by students in that course that the way
they were taught to work such problems was to solve them in two
sections, and that this was further encouraged by asking for
intermediate results like the time at which the highest point is
reached. In the worst cases they reverse sign conventions at the top!

Please, if you teach high school physics, don't do that!

I don't, but they do it anyway. I don't know why.

Steve Clark

Leigh