Why is g maximum at poles and zero at the equator of the earth?
Your question is flawed – g is not zero at the equator. The relationship between gravity and the distance to center of mass of the earth is expressed mathematically as 1/r2, where r is the distance between the center of mass of the two objects. That is called the inverse square law. The earth is shaped as an oblate shpere, where the equator has a slightly larger diameter than the distance from pole to pole. Therefore, an object on the equator is further from the center of the earth than it would be at the poles, and will have less weight, but the same mass. There is also a very slight reduction in weight at the equator due to centripetal force.
