Torsional Waves: The Mystery of the Spinning Chain Sphere Explained

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SUMMARY

The discussion centers on the phenomenon of torsional waves observed when spinning a chain, leading to the formation of an oval sphere with a tail. Users reference the concept of 'standing waves on a string' to explain this effect, noting that increased rotation frequency results in greater amplitude of the standing wave. The conversation also touches on the limitations of the string model due to the lack of elasticity in chains and introduces the catenary line as a potential framework for understanding the behavior of the chain in a rotating frame of reference.

PREREQUISITES
  • Understanding of standing waves and their properties
  • Familiarity with rotational motion and its physical quantities
  • Basic knowledge of catenary curves and their mathematical representation
  • Concept of nodes in wave phenomena
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  • Research the mathematical principles behind standing waves on strings
  • Explore the relationship between frequency and amplitude in rotational dynamics
  • Study the properties of catenary lines and their applications in physics
  • Investigate the differences between elastic and inelastic materials in wave propagation
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Physics students, educators, and enthusiasts interested in wave phenomena, rotational dynamics, and the mathematical modeling of physical systems.

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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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
 
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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.
 
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.
 

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