*********************
I think you are making it too hard, Rick. Leigh asked for an operational
definition. What I offered was such a way of defining weight. I don't care
to know how the bathroom scale works, nor do I think that is important.
The number I get when I stand on it is my weight.
I take the scale with me in the shuttle and "stand" on it and get zero.
Therefore, I'm weightless.
*********************
It seems to me that the above statements fail to provide an acceptable
definition of weight. Consider a reference frame in which Twin A stands
on a stationary scale (Scale A) resting on a horizontal floor and
identical Twin B stands on a scale (Scale B) fastened to a platform that
is accelerating down a frictionless incline, at the bottom of which is a
loop-the-loop. The two scales will have different readings even though
the twins have equal masses. In addition, Scale B's reading will vary
dramatically as it and Twin B traverse the loop-the-loop. Further, if the
incline is not frictionless the readings of Scale B will be different.
If we agree to accept scale readings as the definition of weight then it
seems to me that weight is a peculiar animal and one that is not commonly
accepted anywhere. I am not ready to pass off this definition to my
students. If I am somehow missing the point, please straighten me out.
My recommendation is to avoid using the term weight. It is a difficult
choice, however, because it permiates most of our textbooks. The terms
gravitational force and normal force allow for more clarity.
Gene
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Eugene (Gene) P. Mosca Phone 410-293-6659 Office
Physics Department 410-267-0144 Home
572 Holloway Road 610-683-3597 Summer
U.S.Naval Academy Mailstop 9C, Michelson Rm 339
Annapolis MD 21402 email: mosca@nadn.navy.mil
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