A block with mass m is revolving with linear speed v, in a circle of radius r, on a frictionless horizontal surface (see Fig. 10.48). The string is slowly pulled from below until the radius of the circle in which the block is revolving is reduced to r2.
(a) Calculate the tension T in the string as a function of r, the distance of the block from the hole. Your answer will be in terms of the initial velocity v, and the radius r
(b) Use W = T(r) –dr to calculate the work done by T when r changes from r, to r2
(c) Compare the results of part (b) to the change in the kinetic energy of the block.