Rolling's a combination of rotation (of a radially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that the two are in contact with each other without sliding. This's achieved by a rotational speed at the cylinder or circle of contact which's equal to the translational speed. Rolling of a round object typically requires less energy than sliding, therefore such an object will more easily move, if it experiences a force with a compo… (More on Rolling)