Simple Harmonic Motion Demonstrator

Relation between circular motion and linear displacement on overhead projector.

What It Shows

Uniform circular motion can be shown to be the superposition of simple harmonic motions in two mutually perpendicular directions. This apparatus gives the audience a visual display of how one dimensional simple harmonic motion varies in unison with circular motion.


How It Works

The apparatus is designed to be used on an overhead projector and is animated by a hand-crank.


Setting It Up

Set it out on the overhead projector. If for some reason the alignment of the two dots is off, reposition the glass plate from the underside of the apparatus—the coupling between the circular and horizontal is just friction. Align the two dots with the horizontal one in the center of the circle, as the positioning is more sensitive there.


The apparatus is a good prop to give the student a more intuitive grasp of how the projection of circular motion varies, and therefore is an excellent introduction to the Circular Motion and SHM demonstration. It was originally purchased from Central Scientific Company.