Celtic stone is a solid body that, when placed flat, has a definite line of communication. When you create a spin in the other direction, the energy of the rotational movement turns into a change in energy, and then the change in energy turns into the energy of rotation in the right direction.

Key words: nonholonomic motion, Celtic boat, rattle.

A.V. Karapetyan "Celtic stone" https://teachin.ru/lecture/2019042...

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