I think we have to back off every so often in these discussions and remember
that most people on the list are teaching High School or Intro College
courses. We are struggling to try and shift student's world views (at least
slightly) from their predominantly Aristotelian view to a more Newtonian
view. Few of us have the luxury (in time or student ability) to really move
towards a modern view. The result is that we must focus on analyses from
inertial frames of reference. In fact, IMO, if one can't analyze
accelerating frames from the point of view of a fixed observer, one doesn't
really understand what's going on. In such analyses, there IS a
gravitational force on objects in orbit and the 'apparent shifts in weight
while riding a Ferris wheel must be explained in terms of the 'real' forces
acting on the rider. Later--hopefully in the same course but realistically
only if the student takes more advanced courses--the analysis can move into
the accelerating frame.
In terms of 'g', I try to use a capital script 'G' when talking about the
gravitational field (defined as the Gravitational force per unit mass) and
'g' when talking about the acceleration of a free-falling object. Weight is
a problem but we've had the long drawn out debates about how to define
weight with the 'answer' really depending on whether you are going to stay
in the 'Newtonian box' or expand to the 'Modern/Current box' of
explanations. Which is best for the bulk of our students (who are taking
their 'last' physics course with us) is open to debate--but probably doesn't
matter much. ;-)
Rick
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Richard W. Tarara
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556
rtarara@saintmarys.edu
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