Re: A weighty subject

[Joel Rauber <Joel_Rauber@SDSTATE.EDU>]

Leigh,
Thanks for the succinct summary.  I would like some clarification on a
couple of points you make in your carefully worded definition and how it
relates to some past comments on this thread.  I've interpreted you as being
in the weight is what the scale reads camp, as long as we are careful to not
do the weighing in such situations where non-inertial forces may affect the
scale reading, e.g. weighing the object under-water; I assume you mean that
if we do do such a silly thing, we must take that into account in
interpreting our readings.

> I will point out that I can measure the weight of an
> object in static equilibrium in the laboratory using a scale,
> with the direction of the weight defined as being downward.
>
> Thus the weight W of any object in the laboratory is given by
>
>                         W = mg
>
> g is called "the acceleration of gravity" and on Earth is
> mostly due to Earth's gravitational attraction for the object.
>
> It is important to realize that this constitutes an operational
> definition of g which conforms to the geophysicist's meaning
> of "the acceleration of gravity", conforms to his measurements
> of this quantity, and *it is not equal to the gravitational
> field strength in the laboratory*.

I'm not sure how to relat this to the accelerating upwards elevator. What
would a geophysicist say "the acceleration of gravity" to be in the elevator
reference frame?  I interpret the above statements to confine weight to
effects of gravity, centrifugal forces, and perhaps coriolis and azimuthal
forces? But what of inertial forces caused by accelerating frames that are
not associated with the spinning motion of the earth?  I assume that you
wish to include those as well; so I'd advocate rewording your definition
above in a way to make that clear. (Have I understood you correctly?)

Joel Rauber