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Enforce clockwise spinning, but not counterclockwise

  1. May 4, 2014 #1
    I came across a toy, formed as a rod. When spinning that rod counterclockwise, the behavior is as expected. But turn the direction to clockwise spinning, it immediately slows down and ends up spinning counterclockwise.

    See this YouTube clip. Anyone who has an explantation of this behavior?


  2. jcsd
  3. May 4, 2014 #2


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    Gold Member

  4. May 4, 2014 #3

    Doc Al

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    Staff: Mentor

    It's a really cool toy* called a Rattleback: Rattleback

    *(do not eat)
  5. May 4, 2014 #4


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    So that is a Celtic Stone!

    One of the links shows how to make your own from a spoon.
    http://www.flinnsci.com/Documents/demoPDFs/PhysicalSci/PS10440.pdf [Broken]

    Great after dinner trick on the silverware.
    Last edited by a moderator: May 6, 2017
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