why is earth bulged at the equator?will any one explain me about this?
During the early stages of the earth's formation, as it was bombarded by matter from the rest of the solar system (including whatever produced the Moon), it was much hotter and more of its matter was in a liquid state.
There is a centrifugal force away from the axis of rotation. The spinning on its axis then resulted in a bulging at the equator. It has since become "frozen" in place as the Earth cooled.
The giant mostly gaseous planets Jupiter and Saturn have an even larger equatorial bulge (in percentage terms) for the same reason.