How do the radius of an orbit and gravitational forces affect orbital speed? In this demonstration, a unique hand-held apparatus will be assembled and used to demonstrate orbital speed and centripetal force. Students will use the data collected during the demonstration to calculate the orbital speed of a stopper and to discover the relationships between gravitational force, orbital radius, and orbital speed. A great activity to show students that in order for a planet, star or satellite to maintain orbit, the object must travel at a specific speed. Complete instructions provided.