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Rattleback or Celtic Stone

Notebook is attached to this post. A rattleback is a semi-ellipsoidal top which will rotate on its axis in a preferred direction. If spun in the opposite direction, it becomes unstable, "rattles", stops and reverses its spin to the preferred direction.

enter image description here

This spin-reversal appears to violate the law of the conservation of angular momentum. Moreover, for most rattlebacks the motion will happen when the rattleback is spun in one direction, but not when spun in the other. Some exceptional rattlebacks will reverse when spun in either direction. This makes the rattleback a physical curiosity that has excited human imagination since prehistorical times.

Wikipedia Link References: Link

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POSTED BY: Mariusz Iwaniuk
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enter image description here - another post of yours has been selected for the Staff Picks group, congratulations !

We are happy to see you at the top of the "Featured Contributor" board. Thank you for your wonderful contributions, and please keep them coming!

POSTED BY: Moderation Team

Absolutely marvelous animation - thank you! I did not know it is possible to capture the effect via NDSolveValue. I have not seen a single formula in Wikipedia. Putting your reference from your notebook here:

T.R.Kane and D.A.Levinson, Realistic mathematical modeling of the rattleback International Journal of Non-Linear Mechanics, vol.17, no.3, pp.175[Dash]186, 1982.

This post became quite popular on Reddit / Physics and someone has posted a related paper in the comments:

H. K. Moffatt, Tadashi Tokieda, Celt reversals: a prototype of chiral dynamics, Proceedings of the Royal Society of Edinburgh,138A, 361–368,2008

POSTED BY: Vitaliy Kaurov
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