A spinning cap that reverses direction?

[kyin01]

I was watching a video on where this guy spins a a dial or capsule or a cap (I couldn't really tell, but it was like a long thing cylinder capsule look a like) and well he gave it a quick push and the cap came to a stop and than reverses direction.

What could cause this?


I know that angular momentum is not conserved because of external torque (gravity) and friction causes the thing to come to a halt, but why would it reverse direction. Where does it get the force to reverse direction?

 

[Doc Al]

Rattleback

That's a cool toy called a rattleback. The physics details are non-trivial.

http://en.wikipedia.org/wiki/Rattleback

http://www.4physics.com:8080/phy_demo/rattleback.htm"

 

[charng]

I would say that the spinning cap's change in direction is likely due to conservation of angular momentum. When the cap is initially spinning, it has a certain amount of angular momentum in a specific direction. However, as it slows down due to external torque and friction, that angular momentum needs to be conserved. This means that it will transfer to the cap's surroundings, potentially causing it to reverse direction. Additionally, any slight imbalances or uneven surfaces on the cap itself could also contribute to the change in direction. It is also possible that the cap is not perfectly symmetrical, causing it to spin in a slightly different direction as it slows down. Overall, the exact cause of the cap's reversal in direction may be difficult to determine without further experimentation and analysis.