The Curious Behavior of Spinning Tops

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In summary, the conversation discusses the phenomenon of spinning tops where they start losing speed and then the direction of rotation is reversed just before they stop. The force that causes this reversal is not clear, but it is suggested that it could be due to the torque caused by outside forces such as gravity and friction. It is also observed that after the top stops rotating, it wobbles in the opposite direction of the previous rotation. The direction of precession is determined by the right hand rule.
  • #1
LuGoBi
Wel, this is just crazy.

I've noticed something weird about spinning tops. Most of them start loosing speed, then, just before they stop, the direction of rotation is reversed! Why?! What is the force that makes them stop for a instant and then reverse the rotation?

If you have no idea what I'm talking about, take a look at this video: [Apparently, I can't post URLs to other sites yet, so just go to YouTube and search for a video named "Japanese Koma"]
 
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  • #2
The top spins about it's own axis, but there are forces acting on the top (gravity, friction) that apply a torque to the top. This causes the top to precess, so in addition to the spinning about it's rotational axis, the rotational axis itself turns.

So I think if you could observe the transition in slow motion, you'll find that the top doesn't change directions, but merely that it's precession becomes more pronounced.

Only a guess though.
 
  • #3
Uptade: Just noticed something. The direction of rotation is not reversed. The thing is, after the spinning top stops rotating, it "wobbles" a little bit, and that wobbling IS in the opposite direction of the rotation, but if you look at it carefully, the top isn't rotating anymore, it's just wobbling. Now the question is: why does it wobble, and why does it do it in the opposite direction of the previous rotating motion?
 
  • #4
Ibrits, I hadn't read your message before posting my second one. Seems like our observations agree. Very interesting. Thanks for the answer.
 
  • #5
Allright, this isn't settled yet.

How come, WHILE the top is spinning the rotational axis is also spinning in the same direction of the motion? Then when the top stops rotating the rotational axis reverses it's direction of motion. Why does that happen? And what defines the direction of precession?
 

1. What makes spinning tops spin?

Spinning tops spin due to a combination of forces, including gravity, friction, and angular momentum. When a force is applied to the top, it begins to rotate around its center of mass, creating a gyroscopic effect that keeps it spinning.

2. Why do spinning tops appear to defy gravity?

Spinning tops may appear to defy gravity because of their gyroscopic effect. The angular momentum created by the spinning motion creates a stabilizing force that keeps the top upright, even when it is leaning at an angle.

3. Can spinning tops spin forever?

No, it is not possible for spinning tops to spin forever due to the effects of friction and air resistance. Over time, these forces will slow down and eventually stop the top's spinning motion.

4. What materials are used to make spinning tops?

Spinning tops can be made from a variety of materials, including wood, metal, plastic, and even glass. The choice of material can affect the weight, durability, and spin time of the top.

5. Are there any practical applications for spinning tops?

While spinning tops may seem like a simple toy, they have been used in various scientific and engineering applications. For example, gyroscopes, which operate on the same principle as spinning tops, are used in navigation and stabilization systems.

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