In the previous post, pendulums of the same length (and hence the same natural frequency) oscillated each other. Here, the point is that the pendulums are of slightly different lengths. And yet:

Comprehensive notes can be found in what appears to be the original source of this demo, Bryan Daniels’ senior project at Ohio Wesleyan University.

To my mind this demo isn’t an example of resonance… and that’s a thought we’ll pick up in the next post in this series. Meanwhile, please do share your favourite pendulum demos in the comments. Or, you know, any pendulum-related anecdotes – there’ll never be a better time for those.