A body of mass m whirls around on a string which passes through a fixed ring located at the center of the circular motion. The string is held by a person who pulls the string downward with a constant velocity of magnitude v so that the radial distance to the body decreases from an initial distance r0 to a final distance rf from the center. The body has an initial angular velocity (omega)0. You may neglect the effect of gravity. Show that the work done in pulling the string equals the increase in kinetic energy of the body.

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