Rotational motion is the motion of an object rotating around an axis. There are two types of speed for objects in rotational motion: tangential speed and rotational speed. Tangential velocity is the speed of something moving out of a circular path. Rotational speed is the speed at which something rotates around its axis. An example of this is if you were on the outside of a rotating platform, you would have a tangential velocity and the platform would have a rotational velocity. Tangential speed is directly proportional to the rotation speed at a given distance. An object half the distance from the axis will have half the speed of an object that is at the edge of the rotating platform. Rotational motion also has its own inertia, called rotational inertia. Rotational inertia is that an object that rotates on an axis will remain rotating on that axis until affected by an external influence. Also discussed in this chapter were the centers of mass and gravity, which are both used to describe the point about which an object rotates due to the average position of all the mass in the