[SOLVED] Ball of putty hits rod (rotation) I need help with three problems. For all of these topics we spent a small amount of class time on. And I'm having trouble knowing where to begin. I have posted each on their own thread. A long thin rod of mass of .2 kg and length .04 m lie flat on a frictionless horizontal surface. A ball of putty of mass .05 kg traveling 3 m/s strikes the rod a distance (b) from the end of the stick. Treat the ball of putty as a point mass. Assume all a. upon impact, determine the location of the center of mass b. immediately after impact, what is the angular velocity about the axis through the center of mass of the system? c. using differential calculus, determine the value of (b) that will cause the system to have the greatest angular velocity through the center mass of the system. I'm just looking for the steps that I need to make to solve these questions. Like, how can I arrive to the formula to locate the center of mass of the system. Your help is greatly appreciated.