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Trebuchets are a type of medieval siege engine. Based on the whiplash effect, trebuchets can hurl missiles farther than simpler designs, such as the onager. You can learn more about these weapons, including how to simulate and build them, from the Grey Company Trebuchet Page. The Grey Company is a band of medieval reenactors from Perth in Western Australia.

If you’ve ever tried, and failed, to visualize a Rayleigh wave, Dan Russell can help. An applied physics professor at Kettering University in Flint, Michigan, Russell has put together a series of Acoustics and Vibration Animations. Among his animations are the principal vibrational modes of baseball bats.

“Some are funny. Some are stupid. But at least they are all physically accurate (give or take).” That’s how Harvard University...

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