If ever you’ve been to a science fair or have taken a Physics’ class you’ve probably encountered a pendulum wave. Sometimes just witnessing a physics demonstration can inspire students to look more deeply into conceptual nature of the demonstration and strengthen their critical thinking skills, and this Pendulum Wave demonstration out of bowling balls has no exception.
The Pendulum Wave is a device that provides such an opportunity. It consists of a series of pendulum with increasing periods that when simultaneously released, produce the effect of a changing transverse wave that cycles back to the beginning conditions.
In the video you’re about to see shows a large-scale pendulum wave contraption built on private property in the mountains of North Carolina, near Burnsville. The mechanism relies on 16 precisely hung bowling balls on a wooden frame that swing in hypnotic patterns for a cycle of about 2 minute and 40 seconds.
According to Maria Ikenberry who filmed the clip,
This is a large-scale demonstration of the interaction between period and pendulum length, using 16 bowling balls hung from a wooden frame.The length of time it takes a ball to swing back and forth one time to return to its starting position is dependent on the length of the pendulum, not the mass of the ball. A longer pendulum will take longer to complete one cycle than a shorter pendulum.
As you can see, the lengths of the pendula in this demonstration are all different and were calculated so that in about 2:40, the balls all return to the same position at the same time – in that 2:40, the longest pendulum (in front) will oscillate (or go back and forth) 50 times, the next will oscillate 51 times, and on to the last of the 16 pendula which will oscillate 65 times.
Try counting how many times the ball in front swings back and forth in the time it takes the balls to line up again, and then count how many times the ball in back swings back and forth in the same time. Boy, this will certainly make you feel dizzy!