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Re: increasing, decreasing...



Lately I've been considering the terminology we use in introductory physics
and how it is sometimes confusing and vague and interpreted differently by
physicists. For instance, when you talk about a vector component and
whether it is constant, increasing, or decreasing, are you referring to the
vector component with its sign or the magnitude of the vector component?

I try, like you, to refer to the magnitude. Fortunately for velocity
we have the word speed which means its magnitude. I felt happy this
fall I think that most of my students got it.


A related question on which some students get confused is when I give
a graph of Force versus position (1D) which starts (point A), say,
below the axis, with a small magnitude force, then at the end of the
region of interest (point B) becomes positive, large in magnitude,
and steep. When I asked "Is the particle speeding up or slowing down
as it goes from A to B?" some students talked about it first slowing
down, then speeding up. Now I am careful to ask, "At which point, A
or B, is the speed larger? Explain." I am trying to get them to
answer in terms of work, of course, but some still want the detailed
point-by-point kinematics explanation and generally get the answer
wrong.

Happy New Year.

Hope to see you in Philly, Aaron.
--
Dr. Vern Lindberg New Area Code Nov 15 585- 716-475-2546
Department of Physics Fax 475-5766
85 Lomb Memorial Drive
Rochester Institute of Technology
Rochester, NY 14623
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