Let's say you have a yo-yo that is constructed from two circular masses connected by a small hub. If the radius of the hub is r and the radius of the circular masses is R, how can I find the tension in the string when the yo-yo is released? Assume each circular mass has mass M and the hub is m. I know a bit about angular kinematics and dynamics, but I am having trouble applying that here. I am going to take a guess here and say that the tangential acceleration (the magnitude) is g (9.8 m/s2). The reason I say this is because the yo-yo would have a downward acceleration of g had it not been connected to any string. Because the string is connected, an object on the perimeter of the yo-yo will accelerate in the tangent direction at the same rate as if the yo-yo was in free-fall. Is this reasoning correct? If so, I believe I can make more progess on the problem. Thank you.