Do you get sweets called Skittles in America, or the rest of the world?(adsbygoogle = window.adsbygoogle || []).push({});

We get them in the UK - they're fruit-flavoured sweets in the various colours of the rainbow. The other day, whilst savouring a pack in the cafe at the maths dept, I noticed a particularly strange property of Skittles.

Your average skittle is shaped like you chopped a section off the side of a sphere, then got two of them and stuck them together. It's kind of hard to explain, and I don't know the mathematical name for such a shape, but hopefully this picture will give you the idea:

So anyway. Take a handy Skittle, put it on the table, and then spin it as fast as possible. You'll notice that it starts to wobble a bit, and then all of a sudden it flips up onto its side, so that it's spinning on its edge rather than its bottom! I imagine that this is is just because that's a more stable mode of rotation at higher speeds, but I've been unable to derive that mathematically. So if anyone could help me out, I'd be more than grateful! I'm happy as Larry with Lagrangian dynamics, so feel free to use whatever tools you have at your disposal - I just want an answer!

Ta :)

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# Spinning top question

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