This is a simple simulation of rolling motion. A single point on a rolling object traces out a path known as a "cycloid". Press run and watch as the red point on the circle traces out a cycloid. The motion of any point on the rolling object is actually the vector sum of two velocities: The velocity of the rotating point relative to the axle of the wheel, and the velocity of the axle of the wheel relative to the ground. These two velocities have equal magnitudes. The direction of the velocity of the axle relative to the ground is always to the right, while the velocity of the point relative to the axle is constantly changing. The sum of these two velocity vectors gives the velocity of the point at any given moment. Use the check boxes to see these velocity vectors.