Re: A weighty subject

[Timothy Folkerts <tfolkert@TIGER.FHSU.EDU>]

I just want to make sure I have this right.

> 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*.

Let me define two quantities
    g(1) = GM/R^2    = gravitational field strength
    g(2) = dv/dt     = acceleration of falling object in lab frame

These differ by up to about 0.03 m/s^2, depending on latitude, so
    g(1) = g(2) + v^2/R

Who votes for W = mg(1) and who votes for W = mg(2)?  You seem to be saying
that weight is mg(2).  Or specifically, weigh is the force of gravity minus
centripetal effects due to the rotation of the earth.  So at the poles, W
= mg(1) = mg(2) but at the equator, W = mg(2) = mg(1) - 0.03 m/s^2.

And by the way, which of these two is officially 9.81 m/s^2 ???


Tim Folkerts