Euler’s Disk: Surprising Complexity.

As long time readers will know I’m a fan of simple experiments or demonstrations that have some underpinning scientific phenomenon. It was things like these that first spurred my interest in science, especially since places like Questacon (a must visit place if you ever find yourself in Canberra) were filled to the brim with experiments like them. Thus whenever I find one I feel compelled to share it, not so much for myself but in the hopes that when someone sees it their curiosity will be piqued and they’ll pass that same passion onto others. In that vein I give you Euler’s Disk, one of the most fascinating science based toys I’ve come across:

The disk gets its name from Leonhard Euler, an eighteenth century physicist and mathematician who was behind such revelations as infinitesimal calculus and many other fundamental things. He studied the disk as part of his other research however it wasn’t until recently that they found themselves back in the limelight again. Back in 2000 Cambridge researcher Keith Moffatt demonstrated that air resistance played only a small part in the rate in which the disk slowed down with the vast majority coming from the rolling resistance between the surface and the disk’s edge.

What interest me about it most is the gradual speed up of the revolutions coupled with the increasingly bizarre noise that accompanies it. Then, right at the end when it appears to be spinning at its fastest the disk stops, as if some outside force robbed it of all its momentum instantly. This demonstrates how momentum is conserved as the rate of precession of the disk increases as it spins downward. Explaining the phenomenon though is much harder than just watching it however, which is why it’s such a great scientific toy.

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