1. The problem statement, all variables and given/known data A block with mass m is revolving with linear speed v1 in a circle of radius r1 on a frictionless horizontal surface. 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 v1 and the radius r1. (b) Use W = ∫r1r2T(r) ⋅ dr to calculate the work done by T(r) when r changes from r1 to r2. (c) Compare the results of part (b) to the change in the kinetic energy of the block 2. Relevant equations 3. Attempt at solution I've solved the question except that I thought that T ⋅ dr = Tdr while it was supposed to T ⋅ dr = -Tdr because apparently T and dr are antiparallel. I thought that tension is only in the direction towards the middle of a rope and we're obviously pulling r closer to the middle so how come they are antiparallel?