Purpose: To show that for a particle moving in uniform circular motion, its projection on a diameter moves with simple harmonic motion.

A bicycle wheel with a ball attached to its rim and mounted with its axis horizontal, a motor system for driving the wheel in uniform circular motion, a mass/spring system suspended near the wheel. The equilibrium position of the mass should be level with the axis of the wheel. The entire apparatus is placed on a table with swivel casters.

Set the wheel in motion such that its period is the same as that of the mass oscillating on the spring (probably about 395 RPM on the motor). Hold the mass even with the bottom of the wheel, and release it just as the ball passes. (A little practice is necessary!) Viewing from an edge view of the wheel, you should see the ball and spring moving together in simple harmonic motion. Rotate the table slowly so that all class members have a chance to see the system from an edge view of the wheel.

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