1. The problem statement, all variables and given/known data A puck with mass 0.28 kg moves in a circle at the end of a string on a frictionless table, with radius 0.75 m. The string goes through a hole in the table, and you hold the other end of the string. The puck is rotating at an angular velocity of 18 rad/s when you pull the string to reduce the radius of the puck's travel to 0.55 m. Consider the puck to be a point mass. What is the new angular velocity of the puck? 3. The attempt at a solution So we clearly have a centripetal force here caused by the pull of the string. ooo... definitely just realized that I was given the mass. I was going to ask how in the world is the problem solvable without it. let me work some more and see what I come up with. So, I believe that the centripetal acceleration is linear not angular. I need to somehow relate this linear acceleration to the change angular velocity and radius... By the way, is it necessary to consider moment of inertia, or does it not matter because the object is already in motion? But since the object is accelerating... Are there any good websites that explain moment of inertia nicely? I still do not completely understand it.