Register to reply 
A spinning wheel 
Share this thread: 
#19
Feb1214, 02:54 PM

Sci Advisor
Thanks
P: 1,908

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

Engineering
Sci Advisor
HW Helper
Thanks
P: 7,157

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

Sci Advisor
Thanks
P: 1,908

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

P: 10

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. 


Register to reply 
Related Discussions  
Induced EMF in a spinning wheel  Classical Physics  2  
On a spinning wheel  Special & General Relativity  9  
Spinning bicycle wheel  Introductory Physics Homework  1  
Spinning wheel  Introductory Physics Homework  2  
Spinning wheel problem  Classical Physics  1 