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# more of R& M and such

Rick said,

Personally I think there is some very important physics tied up in this
discussion with 'clearly' some mistakes being made by some of us in our
instruction. The thread, while long-winded, is sorting out some of
these.

I agree, it is long winded, and again thanks to all who have beared with it.
I've been doing some literature reading because of this; which I should've
done long time ago and will comment when I have time on what I have read.

Just seems to me you have gotten too complicated here. One of your
purposes for introducing 'forces' into the non-inertial frame was (I
thought) to preserve a 'Newtonian' view. Now you're willing to abandon
the third law where convenient. I think your methodology involves too
many 'ifs', 'ands', and 'buts'. To adopt the 'Marlow' view for
introductory work, I need only preserve gravity as a 'traditional'
force--thus only one 'but'! ;)

Generally, for introductory work I agree, and I adopt the Marlow view; I
start with an inertial frame of reference . . .

But I have seen problems where I found it easier to go the other way, and in
advanced work I think it happens more often; for example the study of
Oceanography.

I may misstate here : The only "but" I've given when I analyze in a
non-inertial frame is to forego applying the 3rd law to the apparent forces.
Which means treat them as external forces to your system. This is something
we already do in the analysis of many problems in inertial frames; see for
example my addendum. And doesn't seem more complicated particularly then
what you would already do in an inertial frame for that problem. (I admit
it was a complicated problem to start with.)

Actually my preferred way to work with the non-inertial frames is NOT to
analyze from within. That is, we acknowledge the sensations within the
accelerating frame BUT then analyze it from the point of view of the
inertial frame. This then allows the student to 'see' that the effects
felt ARE 'backwards' from the real forces causing them. This seems to
work reasonably well in my classes!

This is my preferred way to work the simple situations that we deal with for
the most part in introductory classes as well! I'm not trying to say that
analyzing the non-inertial frame is always the preferred way or even most of
the time the preferred way. Simply that it is logically consistant and
possible to do so.

Actually I'm saying a little more, I'm saying that objects behave in
non-inertial frames as if those apparent forces really are there. "behave"
means the measurements you make of the objects in that frame of reference.
What measurements are admissable: the position as a function of time for
the objects in question. We then use kinematics to infer the velocity and
acceleration as functions of time and dynamics to determine combinations of
those quantities and the mass; namely momentum, kinetic energy. From
momentum and kinetic energy we infer the existence of potential energy
functions for some of the forces, but not for others. so forth and so on.

Excuse if the above paragraph is written rather oddly, as it was written in
haste.

Thanks for listening to the long windedness and putting the proverbial 2
cents

Joel Rauber
rauberj@mg.sdstate.edu