Ball on turntable rotates beneath synchronized pendulum .

Simple Harmonic Motion and Uniform Circular Motion: Simple Pendulum, and Ball on Record Player. When the length of the pendulum and the speed of the record player are set correctly, the periods of both are the same, and the shadows match up on the screen. (The turntable has a variable speed control to fine-tune the period). Note: The point source light is actually mounted on a large floor stand about 5' in front of the lab bench to get the source farther from the demo.