If I start spinning a raw egg very slowly in place, why does its angular velocity increase spontaneously? This is something I noticed the other day while cooking. It doesn't do the same thing with a hard-boiled egg, so I assume it has to do something with how the contents of the raw egg are distributed during the spinning process, but I was wondering if someone could fill in the details.
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Qmechanic
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Dargscisyhp
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Relared: http://physics.stackexchange.com/q/150795/2451 , http://physics.stackexchange.com/q/119394/2451 and links therein. – Qmechanic Jun 13 '15 at 17:46
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This only works if you spin it up & then briefly stop the shell, which doesn't stop the fluid contents from rotating. – Carl Witthoft Jun 13 '15 at 21:16
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1@CarlWitthoft I was able to do it as he described, though the effect was rather more subtle than the way you describe it. – dmckee --- ex-moderator kitten Jun 14 '15 at 18:24
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Related : Will a boiled egg or a raw egg stop rolling first?: http://physics.stackexchange.com/q/19260 – sammy gerbil Jul 11 '16 at 19:06
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Never seen that before, so I just tried it. Cool.
I believe that the membrane between the yolk and the white is elastic, so when you first, gently, give the egg a little angular momentum, you are only spinning the white. As the yolk catches up the effective moment of inertia drops, and conservation of momentum therefor implies a higher angular velocity.
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This appears to be reasonable for a short impulse, but for an application of force over a second would mean that the yolk doesn't rotate for most of that time. – LDC3 Jun 13 '15 at 17:30
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@LDC3 Well, yes. And I only tested it with about a one radian twist given in about half a second. You need a pretty smooth surface to observe the effect under those condiction. – dmckee --- ex-moderator kitten Jun 13 '15 at 17:35