The simulation on Page 2 shows the motion of a point fixed on a rolling spool. The motion of the point is the superposition of the revolving and translating motions of the spool. This kind of a motion is called cycloidal motion. The spool point's motion can be understood in terms of the Galilean transformations of position and velocity.

Detailed information on how the applet functions and a lesson with exercises to be carried out with the applet are available under Applet Help from the applet's Help menu.