Question

What is the effect of the shape of Earth on value of '$g$'?

Answer 1

As we know $g=\frac{GM}{R^2}$

hence $g\propto \frac{1}{R^2}$

Thus, acceleration due to gravity at a place is inversely proportional to the square of the distance of the point from the center of earth. Now, the earth is not perfectly spherical. It is flattened at the poles and elongated on the equatorial region is approximately $21$ km more than that at the poles. Hence $g$ is maximum at the poles and minimum at the equator.