Question

why we weigh less at the poles than on d equator?

Answer 1

you should weigh marginally less at the equator

the earth's bulge, which is pretty tiny, means you are that bit further from the earth's centre of mass. plus the rotation of the earth means that you are being thrown outwards...don't want to get into an argument about centrifugal forces so choosing my words carefully :p

the effect is very small compared to normal g = \(9.8m/s^2\),

eg the contribution of earth's spin:

\(\large \omega^2 r = (\frac{2 \pi}{24 \times 3600})^2\times 6.4 (10^{6}) = 0.03m/s^2 \)

the radial bulge is around 20km, compared to a rad of about 6,400km, and difference comes out at c.\(0.06m/s^2\)....