1. The problem statement, all variables and given/known data A particle of mass m is moving on a frictionless horizontal table and is attached to a massless string that passes through a tiny hole of negligible radius in the table, and I am holding the other end of the string underneath the table. Initially the particle is moving in a circle of radius r0 with angular velocity ω0, but I now pull the string down until the radius reaches r. How much kinetic energy did the particle gain? 2. Relevant equations 3. The attempt at a solution I integrated to find the potential energy and I know the force is conservative for the kinetic energy = -potential energy. Is that right? I also figured that the final angular velocity is the same as the initial angular velocity. Is that correct?