Thanks to these 16 bowling balls hung from a 20 foot wooden frame in the mountains of North Carolina, we can see what a large-scale pendulum wave apparatus looks (and sounds) like. Filmed by Maria Ikenberry, she also provides some details behind the physics lesson:
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. 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 (though it’s much harder to keep your eye on the ball in back!).
The experiment isn’t a completely controlled one — the flexing wooden frame, any friction from breezes, and touching the tone-making pipes with each pass, as examples, become factors affecting each pendulum’s swing — but it’s still a feat of measurement and science demo enthusiasm! The “whoaaas” and “aaahs” are proof of its impact.In the archives: Citadel Physics’ Wave Pendulum, a Harvard Pendulum Waves demo, more pendulums, more rhythm, and more demonstrations.