Rattleback

http://www.shinyshack.com
Spin it clockwise and watch it stop and spin the other way

Category:

Entertainment

Tags:

• rattleback
• spinning
• celt

[buyunz]

Can someone please explain to me why such a phenomena occurs?

[ShinyShack]

The spin is caused by the specific alignment of the long axis of the ellipsoid in relation to the the long axis of the flat top - ie. they're not parallel so the rattleback is predisposed to spinning in one direction.

[buyunz]

Thank you for answering my question, does that mean that rotational kinetic energy for spinning in one direction is somehow converted into spinning in the counterdirection, and as it is not symmetrical, it is therefore not really a contradtiction to the conservation of angular momentum?

[ShinyShack]

Our resident physicist says: "Strictly speaking, it's the kinetic energy contained in the oscillations (rocking) of the rattleback that is transformed into rotational kinetic energy. Angular momentum is conserved because as the rattleback spins, the earth spins a little in the other direction (but a tiny amount), because they are coupled by friction."

[The3rdPlateau]

@ShinyShack but what if the Earth's rotation were to correspond with the rotation of the rattleback's direction before it turns itself around...and couldn't this be achieved in the opposite hemisphere?

[rekingooo]

It has nothing to do with earth rotation

[buyunz]

Thanks, that's made it much clearer.