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Re: [Phys-l] definitions ... purely operational, or not



In response to Rick T:

I would say these two choices--stay in the 'fixed'
frame for analysis or freely move between frames (again for analysis) is
what drives this constant debate about the meaning of 'weight'. We all-
-and
the older ones amongst us ;-) are firmly entrenched--in our preferences!


I think you've correctly analyzed what drives the discussion. Is it fair to say that you are using the "Bartlett" definition of weight, but with the proviso that one always choose the earth surface frame of reference? (I don't think you are equating weight with GMm/r^2, i.e. Newtonian gravitational force, or are you?)


To me the great
advantage in a typical physics major curriculum is the spiral approach.
One
can learn the Newtonian model and work mostly at the Algebra/simple
integral
level of sophistication in first year courses and then get much more
sophisticated in second year mechanics, then really sophisticated in
graduate level mechanics. Same for E&M and Thermal. KISS is a very
appropriate approach for 1st year courses and almost a necessity in
courses
for non-science majors (general education science courses) and probably
equally appropriate for pre-med and engineering physics courses. This
doesn't preclude doing some work from accelerating frames in such
courses,
but should allow for the choice to back off and always look at the
accelerating frame from the fixed frame. Look at the falling elevator
from
someone in the building, the space station from the point of view of
someone
on earth--then explain in those terms what is experienced by those in
the
accelerating frames. I would say these two choices--stay in the 'fixed'
frame for analysis or freely move between frames (again for analysis) is
what drives this constant debate about the meaning of 'weight'. We all-
-and
the older ones amongst us ;-) are firmly entrenched--in our preferences!

Rick

Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, Indiana
*******************************************
Free Physics Instructional Software
www.saintmarys.edu/~rtarara/software.html
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