This is one of the simplest but most captivating physics videos I’ve ever seen:
Each pendulum is at a slightly different length – not just for the visual effect, but it gives them different phasesperiods/frequencies [Seth, the Physicist in Ask a Mathematician/Ask a Physicist wrote me to correct this – Thanks Seth!]
Fifteen uncoupled simple pendulums of monotonically increasing lengths dance together to produce visual traveling waves, standing waves, beating, and random motion.
For more details see http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&pa…
The period of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it executes 51 oscillations in this 60 second period. The length of each successive shorter pendulum is carefully adjusted so that it executes one additional oscillation in this period. Thus, the 15th pendulum (shortest) undergoes 65 oscillations.
This seems easy enough for middle school students to set up and learn from. Our friends at Ask a Mathematician/Ask a Physicist just had a post: Cheap experiments and demonstrations for kids. I think this would be a great addition.
(Via Richard Wiseman)