Question

Why weight near to poles of earth are comparable less thsn in equator region

Answer 1

Weight of object=mg. If g is less then the weight is less.

Why g is less at the equator -

1. The shape of the earth is oblate spheroid. That's why the radius at the equator is more. Thus, g is less at equator.
2. The centrifugal force( Mw^2 R) is opposite to g at equator(the angle between them being 180°). Since forces are vectors and the resultant vector is minimum when the vectors are opposite to each other, g is minimum at equator. If the earth rotated extremely fast then the centrifugal force and g would have cancelled each other out at equator !

Earth is not perfectly spherical.

It has less radius on poles and More on equator

So due to less radius on poles the g experienced is More as the surface is closer to the center of earth compared to the equator .

Second reason is that Earth is spinning with more angular velocity at equator are it decrease as we move towards the poles.

This increased angular velocity at equator produces a force a outward centrifugal force which decreases the effect of g