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Re: [Phys-l] Weightless



Have you ever asked your students these questions? Do some peer
instruction, and you might be surprised at what they really think. I doubt
that high school students in Pomona are any different from those here in
Princeton. Everyone struggles with these concepts.

Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:
Anthony Lapinski wrote:

People in their everyday experience think a bathroom scale measures
their
downward weight.

I don't think the average person would think to consciously qualify
their weight as "downward." What they think (correctly in my--
mainstream, I think--opinion) is that the scale measures their weight.

And so when the scale reads zero for the astronauts, they
think g = 0!

I'm even more skeptical that the average person would consciously
think something like that. (On the other hand, if they did, they
would also be correct in my opinion! Here I'm prepared to concede
that my opinion may not be mainstream or even pedagogically sound
even if it is in agreement with our current best theory of gravitation.)

Lots of confusion and misconceptions with this with ALL
people.

I'm still not convinced.

I guess one could never have a true weight equal to zero unless you
are
"very far" from all objects (so that g = 0).

By "true weight" I assume you mean the same thing as "gravitational
force" so why not just call it that? And at the risk of sounding
like a broken record (a train that left the station long ago!), I
will point out once again that, according to the current best theory
of gravitation, there is no less and no more "gravity" (in the sense
of gravitational force or gravitational force field) in deep space
than there is here on Earth or any where else in the universe.
According to the principle of equivalence, that aspect of gravity IS
inertia and vice versa. We make our own gravity.

Standard disclaimer: I'm not promoting the idea that we teach
students general relativity. I just think there's room within our
professional ranks for a little more appreciation of the deep and
beautiful message conveyed by the principle of equivalence.

John Mallinckrodt

Professor of Physics, Cal Poly Pomona
<http://www.csupomona.edu/~ajm>

and

Lead Guitarist, Out-Laws of Physics
<http://outlawsofphysics.com>
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