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Re: What is weight? (was Re: Internal or external?)



----- Original Message -----
From: Leigh Palmer <palmer@SFU.CA>

It seems to me that the *only* folks out of step with the rest of
humanity on this issue are the introductory teachers of physics.
Perhaps that is why there is such a fuss over this concept among us!

Leigh


Maybe I've misread some of these posts (I read them very quickly), but I've
interpreted what has been written as saying that both engineers and chemists
tend to agree with W = mg. The chemists are smart enough to realize that
their scales don't always read mg due to extra forces (like buoyancy) and
must therefore make corrections. I also suspect that the 'man in the
street' considers weight to be a property of the object--more akin to mass,
rather than what the scale reads. In other words, I don't think 'we'
introductory teachers of physics are such an isolated minority. ;-)

You've missed the chemists' point. Their calculations are intended to
restore the value which will be measured by a balance comparing masses
by gravimetric* means. They do want to find mg, but their g is the
same one I've been talking about; it is not the force of gravity.

Leigh

*This is the same sort of misnomer as "gravimeter". A pan balance is
conventionally used on the surface of Earth. It compares the inertial
forces exerted on two masses, not the gravitational forces alone.