1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution I tried with the conservation laws. Angular momentum conservation won't work. To use energy conservation, I need the force pulling up the string but I don't have it. The force in the given case is tension but the tension continuously changes and I am not sure if the tension force is the conservative one. I don't have any idea about how to start making the equations. :( Any help is appreciated. Thanks!