bowling balls

Got to see this demonstration of physics by bowling balls this weekend. It’s beautiful and cool. Watch all the way to the end to see the balls move back in phase with each other, as they are at the start. In between, it moves from beautifully ordered to apparent chaos and back, again and again.
Because this video has been very popular, here are answers to some common questions:
** What am I seeing? How does this work? **
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!).
** Why are they not perfect at the end? **
This large frame is built from wood and is outdoors, which means it expands, contracts, and flexes. Because the position of the frame changes, the cycle lengths are not perfectly aligned. Over time, the minor differences become more pronounced.
** Where is this? **
This was built on private property in the mountains of North Carolina (United States), near Burnsville. It is not open to the public.
** Can I get a copy of this video to use in my classroom? **
Yes. But I don’t have a link for you yet. Come back in a day or so to get the link here.
** How can I make my own? Where can I learn more? **
Here are some links to information about the physics behind this demonstration. There are some small scale versions of this demonstration that can be purchased commercially as well, but if you want a 20’ version like this, you’ll have to make your own! I didn’t make this and I don’t have plans for it, but work through the physics at these links and design your own – you’ll learn a lot about physics, math, and construction!

http://www.arborsci.com/cool/pendulum-wave-seems-like-magic-but-its-physics
http://io9.com/5825639/a-simple-physics-demonstration-that-shows-why-science-still-sometimes-seems-like-magic
http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pageid=icb.page80863&pageContentId=icb.pagecontent341734&state=maximize&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent341734
http://scitation.aip.org/content/aapt/journal/ajp/69/7/10.1119/1.1349543?ver=pdfcov

Published on Mar 8, 2012

A pendulum wave with 16 bowling ball pendulums of different lengths, Doc’s Pasture, Celo NC. Another good view with people lying undeneath: http://youtu.be/RNxqEudZ-hE The math behind this and some more details are at: http://celophoto.blogspot.com/2012/03…

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