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[Phys-L] Re: A Third law question



At 23:18 -0500 10/12/05, John Clement wrote:

There is evidence that momentum should be taught before energy and that 1-D
examples should be exhausted before going on to 2-D examples. Beyond this
there is little evidence for other major sequence changes. The 1,2-D
problem has been confirmed by McDermott in the latest AJP and has been
previously reported by Laws et al.

I agree with this as well. Our course starts with one-dimensional
analysis, and since it is designed for students who have not already
had trig, they only get that much 2-dimensional stuff as they
absolutely need to understand simple circular motion (no moments of
inertia). Later, when they have had trig, and we study wave motion,
we can use sines and cosines, but until then, there is very little of
two dimensional motion.

I don't think anything is lost. They get some examples of inclined
planes (non-trig examples, however--they have to do everything
geometrically), and see a little bit of trajectories, and when they
have trig, these things should become conceptually simpler to
understand, but it is applying the ideas after they have already seen
them in a one-dimensional context.

Hugh
--

Hugh Haskell
<mailto:haskell@ncssm.edu>
<mailto:hhaskell@mindspring.com>

(919) 467-7610

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