Fall Into A Trance Watching This Pendulum Wave Of Bowling Balls

Because a pendulum's oscillation frequency depends on its length, not its mass, you can use different colored bowling balls for a pretty effect.

Happy Monday! How about some simple physics to get your day started? We very much enjoyed this video, posted yesterday, of a giant outdoor DIY pendulum toy made with bowling balls. The toy even makes music, via pipes mounted in the ground. Cute!

https://www.youtube.com/watch?v=YhMiuzyU1ag

The structure works just like smaller pendulum wave toys. Each bowling ball’s string is a slightly different length, with the shortest string mounted at one end of the series, the next-shortest string mounted next to it, and so on until the longest string is found at the other end. For best results, the string lengths should follow a particular formula, as described in this short paper published in the American Journal of Physics in 1991:

The ground underneath the outdoor structure is actually slanted, to accommodate the different string lengths, while keeping the bowling balls all about the same height off the ground. Jeff Goodman, a lecturer in education at Appalachian State University, designed and built the structure with friends.*

Want to make your own mesmerizing physics demo in the forest? You could start with a desktop version, so you can figure things out on a more manageable scale. There are a number of instructions online for making indoor-sized wave pendulum structures. We didn’t immediately find any instructions for a structure large enough to hold bowling balls, however, which would require a little engineering to ensure the frame is strong enough. Let us know if we’ve missed any instructions that are already out there…or if you’ve made this on your own.

*Updated September 12, 2014: We previously guessed that the top of the bowling-ball pendulum structure was slanted to accomodate the different string lengths. Goodman wrote to us to correct us. Our thanks!