I am wondering, when solving rigid body exercises, how can I express the relationship between linear and angular acceleration for a general case? E.g. what would be the linear acceleration in function of the angular one of a 1m rod that is rotating through a fixed point 0.6 m away from its mass center? And what about the case of a yoyo? Thank you for your help!! I am really confused with this. Edit: I know the basic relation a=α∗R, but I am confused as to how to choose R and my textbook is not helping.