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A spinning wheel 
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#19
Feb1214, 02:54 PM

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Define a circle with radius r, centred at the origin, x^2 + y^2 = r^2
The centre is specified as a point, P(x,y), where x = 0 and y = 0. Rotate that circle continuously about it's centre. The x and y coordinates of the centre do not change with that rotation. Therefore the point at the centre is not moving. In mathematics, a point does not have an orientation. 


#20
Feb1214, 03:06 PM

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The mathematical reason is that strain is not a property of an isolated point of material, it is also property of the the material close to that point. And if we are talking about quantum mechanics, a question about "a particle in the center of the wheel" is rather meaningless. 


#21
Feb1214, 04:05 PM

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The question becomes one of the difference in definition of a particle and a point. As you zoom in closer, does the particle at the centre ever become a mathematical point at the centre. I believe a particle always has orientation while a mathematical point never does. Also, a particle always has a mass, a point never has a mass.
At some molecular scale the physics of shear as a bulk property will cease to be valid. It will be replaced by a space frame of directional bonds. That space frame and each part of it, is also a directed particle. No matter how closely you zoom in, a physical particle will always be a particle with an orientation and mass. It can never become a mathematical point without orientation or mass. 


#22
Feb1314, 06:33 AM

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Now I realize that no one should think about a deadcentre point when it comes to a spinning/rotating disc/wheel. Even though the linear speed is zero at the dead centre, logically thinking, zero speed is never reached in angular speed, no matter how much one enlarges the deadcentre point. 


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