Irodov Problem 1.128

The centrifugal force of F = will always act radially outwards in the rotating reference frame. As the mass moves the work done by the centrifugal force is . The vector dr will have two components a radial component dr (corresponding to the radial motion of the body) and (corresponding to the tangential motion of the body). Since, F acts only radially, the dot product of the tangential part of the bodies motion and F will be 0. Hence we have,