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The rotating earth is a non-inertial frame of reference. What I have
been referring to as weight measured by the bathroom scale is the normal
force exerted by the scale. In an inertial frame of reference, N=mg
numerically.
F(net) = ma (in general)
or N-mg=ma
If a=0 as in static equilibrium, then
N-mg=0
and N=mg
However, the rotating earth is a non-inertial frame of reference and we
must write
N-mg=-mv^2/r
or N=mg-mv^2/r .
Since the last term is small, I said that N was nearly equal to mg.
Roger Pruitt