Demonstrations of Simple Harmonic Motion

Mass on a Spring

This demonstration shows the motion of a mass connected to a horizontal spring. This motion was started by displacing the mass from its resting position (when the spring is neither compressed or stretched) and then releasing it.

Pendulum

This demonstration shows the motion of a mass connected to a (massless and inelastic) spring. This motion was started by displacing the mass from its resting (lowest) position and then releasing it.

Uniform Circular Motion

This demonstration shows the uniform motion of a particle along a circular trajectory. This type of motion results when the particle is subject to a central force, e.g., from the tension in a string or the gravity of a central mass.

What Do These Motions Have in Common?

Compare these three motions shown together in this demonstration. What do they have in common? (Hint: compare the motion of their shadows.)

Simple Harmonic Motion Revealed

The common feature in these three motions is called Simple Harmonic Motion. We can capture its essence by tracing out the position of the shadow over time as shown in these demonstrations of a:

What Does This Have to do with Sound?

When a sound is produced by the air disturbances of a solid body undergoing Simple Harmonic Motion, then the air particles along the direction of propagation also undergo Simple Harmonic Motion.

This simulation shows a solid object (e.g., the wooden body of a violin) subject to elastic (spring-like) forces and undergoing Simple Harmonic Motion. The highlighted test particle in the middle of the screen also shows the same motion.