The motion of an object that spins on a axis contained in the object . During rotational motion all points in the body move in circles and the center of all of those circles is on the axis of rotation.
Angular motion is a term used interchangeably with rotational motion.
An angle , with its vertex at the center of a circle, that would cut off , on the circle, and arc whose length is as long as the radius of the circle . An interaction between two objects where one object strikes the other object . This implies that a center of mass is the point in an object where all of its mass seems to be located. The point in an object where the force of gravity seems to act . Unless the object is so large that the acceleration of gravity changes from one part of the object to another, the center of gravity and the center of mass are the same point in the object.