... Uniformly moving frames of reference experience no new forces. ... If we want to express the equations of motion in their own frame of reference , we must always add "inertial forces" to represent the effects of their acceleration. ... The centrifugal force is needed to describe the same motion, using coordinates, velocities and accelerations of a rotating frame of reference. ... Terms: inertial force, accelerated frame of reference, rotating frame of reference, centrifugal force, bulge of the Earth...