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Re: No definition of weight



While I understand the reasoning for your concern and avoidance of the
word "weight" it seems to me that you cannot ignor that the word exists
in our students vocabulary. If you are concerned with
connecting their inclass learning with the world they live in, you have
to find a way to connect their concept of weight with something that
they talk about in class.
Do you do that, and if so how?

cheers,

joe

On Fri, 8 Feb 2002, Laurent Hodges wrote:

For many years (off and on - not continuously) I have taught introductory
physics and I do it without using the term "weight" at all. (Or only in
telling the students to ignore the term in their textbook, and use
mg/gravitational force instead.) All my free-body diagrams include a
gravitational force mg (g being due to everything in the universe), and
that's what I call it. No W vector, so W is only work. When we discuss
moving and/or accelerating elevators, we may talk about the upward normal
force of the elevator floor on a person, but I don't call that "apparent
weight" either.

I can then ask the question, what is meant in ordinary English by the
feeling of "weightlessness" in a spaceship orbiting the earth? No
gravitational force? No! No normal force pushing on you? Yes.

In mechanics we find it useful to clearly define "velocity" and "speed" in
the physics sense, which may not coincide with the ordinary English uses of
these terms. But I see no purpose in using the term "weight." It
unnecessarily confuses students.

Colleagues who teach with me in the same course accept this easily, but
most of my colleagues use "weight" when teaching introductory physics.

Can't we get rid of the term?


Laurent Hodges, Professor of Physics
12 Physics Hall, Iowa State University, Ames, IA 50011-3160
lhodges@iastate.edu http://www.public.iastate.edu/~lhodges


Joseph J. Bellina, Jr. 219-284-4662
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556