Torsional Waves: The Mystery of the Spinning Chain Sphere Explained

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In summary, the conversation discusses the phenomenon of a chain spinning quickly, producing an oval shape with a tail at the end. The faster the chain is spun, the greater the horizontal radius of the shape. The conversation also explores the concept of standing waves on a string and the possibility of the 'catenary line' principle being applied to explain the effect in a rotating frame of reference.
  • #1
cmdr_sponge
has anyone ever noticed that if u hold a chain at one end and spin it round real fast u get a kind of oval shpere produced but with a tail at the end. the faster you spin the chain the greater the horizontal radius of the 'shpere'. i thought really hard about this but i can't work it out.

atm i think tht the point where the shpere is completed and the tail begins is some kind of node.

how can you explain this effect and work out where the 'node' will be produced?
 
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  • #2
Hi cmdr_sponge,
I think the phenomenon you refer to, can be basically described as 'standing waves on a string'. Here's a nice site:

http://id.mind.net/~zona/mstm/physics/waves/standingWaves/standingWaves1/StandingWaves1.html [Broken]
 
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  • #3
i have studied standing waves. the only thing that confued me was that when the frequency of rotation increased the 'amplitude' of the standing wave increased, rather than when the amplitude of the driver is increased. i know that linear physical quanties (momentum etc) have related quantities in circular motion, could this have nething to do with it.
 
  • #4
Maybe the 'string' model is not so good since a string has elasticity and a chain has not.
I had another idea. You know the 'catenary line'? It's the form a chain suspended at both ends, takes on. It has minimum potential energy and can be exactly calculated (it's basically ex + e-x).
Maybe if you apply this principle to a rotating frame of reference, you get what you want.
 

1. What are torsional waves?

Torsional waves, also known as shear waves, are a type of mechanical wave that travels through a material by twisting or shearing it. They are caused by a combination of compressional and shear forces and can travel through solids, liquids, and gases.

2. How are torsional waves different from other types of waves?

Torsional waves differ from other types of waves, such as transverse and longitudinal waves, in their mode of propagation. While transverse waves move perpendicular to the direction of the wave, and longitudinal waves move parallel to the direction of the wave, torsional waves move in a twisting motion.

3. What is the mystery of the spinning chain sphere?

The spinning chain sphere, also known as the Newton's cradle, is a popular toy that demonstrates the conservation of momentum and energy. However, the exact mechanism behind the movement of the spheres has been a mystery for many years.

4. How does the mystery of the spinning chain sphere relate to torsional waves?

Recent research has shown that the movement of the spheres in the spinning chain sphere can be explained by the propagation of torsional waves. As the spheres hit each other, they create torsional waves that travel through the chain and cause the spheres to move in a coordinated and predictable manner.

5. What are the practical applications of understanding torsional waves?

Understanding torsional waves has many practical applications, including in the fields of seismology, non-destructive testing, and earthquake engineering. Torsional waves can also be utilized in the design of mechanical systems and structures to improve their stability and efficiency.

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