The graphing window displays a circle of radius a in green, its center in purple, a radial line segment of length b in cyan, and a point (a "light") at the end of that radial line segment in yellow.

Set the wheel radius a and the radial setting b of the light using sliders at the bottom.

Animate the rolling wheel using the [>>] key, or control its position by grabbing the theta slider, by using the [<], [>] keys, or by dragging the cursor over the graphing window with the mouse button depressed.
The value of theta, the angle of rotation, ranges from 0 to 6π if a < 1 and from 0 to the value of θ at which the center has x coordinate 6π if a > 1.

Click [reset] to reset θ to zero.

Select the toggle [trace] to cause the light to leave a yellow trace and of the center of the wheel to leave a purple trace.

Select the toggle [velocity vector] to display the velocity vector in red.

Roll the cursor over the graphing window to create crosshairs and a readout of the cursor position.

c 2001 H. Hohn