# This Object ALWAYS Spins Counter-Clockwise, why?

• jaridwarren
In summary, the author is trying to determine why an object always spins counter-clockwise. He found an article that explains the history of the rattleback toy and provides some leads on how to fix it.

#### jaridwarren

Hey guys,

I've read these forums a ton over the years and found everything I needed merely by searching. But alas, the day has come where I've needed to create an account to help me with a problem.

I have to determine why this object ALWAYS spins counter-clockwise. Whether you spin it clockwise, tap it, push it - it doesn't matter... pretty bizarre.

Here are some picture and appreciate the help:

jaridwarren said:
Hey guys,

I've read these forums a ton over the years and found everything I needed merely by searching. But alas, the day has come where I've needed to create an account to help me with a problem.

I have to determine why this object ALWAYS spins counter-clockwise. Whether you spin it clockwise, tap it, push it - it doesn't matter... pretty bizarre.

Here are some picture and appreciate the help:

What you said kind of doesn't make sense. When you spin it clockwise it spins counterclockwise?

And can you give more details about what it is? Where did you get it?

In Wales, it is called a rebellious celt. To us, it's the rattleback. "It" is a long, thin plastic toy with a base shaped like the hull of a boat. When you spin it one way, it turns a few times before the ends start to rattle up and down. The more it wobbles, the slower it rotates - until it stops spinning altogether. Finally, it starts to spin in the opposite direction. What could possibly cause this?

The first attempt to analyze rattlebacks was around a century ago. In the mid-1980s, two detailed mathematical analyses were done: one by Hermann Bondi (then Master of Churchill College, Cambridge) and the other by Mont Hubbard (Professor of Mechanical Engineering at the University of California, Davis).

In the mid-1980s, two detailed mathematical analyses were done: one by Hermann Bondi (then Master of Churchill College, Cambridge) and the other by Mont Hubbard (Professor of Mechanical Engineering at the University of California, Davis).

The author of that page missed Thomas R. Kane, the author of modern dynamics theory ("Kane's method"). He and David Levinsion published "Realistic Mathemaical Modeling of the Rattleback" in 1982. This paper preceded both Hubbard's and Bondi's papers.

## 1. What causes this object to always spin counter-clockwise?

The direction of spin is determined by the object's angular momentum, which is the amount of rotational motion it possesses. This object likely has a consistent force acting upon it in a counter-clockwise direction, such as friction or torque, causing it to spin in that direction.

## 2. Is there a specific reason why this object doesn't spin clockwise?

Yes, as mentioned before, the object's angular momentum determines its direction of spin. If the object had a greater amount of force acting upon it in a clockwise direction, it would spin in that direction instead.

## 3. Could the direction of spin change at any point?

It is possible for the direction of spin to change if the forces acting upon the object change. For example, if a force in the opposite direction is applied to the object, it may start spinning in the opposite direction.

## 4. Are there any external factors that could cause the direction of spin to change?

Yes, external factors such as changes in temperature, pressure, or applied forces can impact the direction of spin. Additionally, if the object's center of mass is not perfectly aligned with its axis of rotation, it may cause the direction of spin to change.

## 5. Is the direction of spin consistent across all objects?

No, the direction of spin can vary depending on the object's shape, mass distribution, and external forces acting upon it. Some objects may spin clockwise, while others spin counter-clockwise, and some may even spin in both directions at different times.