Calculating Maximum Revs/Sec w/ Speed c & Circumference of Disk

[QuantumHop]

I'm assuming the maximum number of revolutions per second for a disk is defined as speed c divided by the circumference of the disk, eg a disk with a circumference of half a meter is allowed to rotate twice as fast per second as a disk with a circumference of one meter.

C = circumfrence of the disk
c = speed of light
mrps = maximum revolutions per second (not meters per second)

So is the value of mrps nice and simple : mrps = c / C

Or are there more complicated relativistic affects, for example does the circumference shrink due to length contraction.

 

[pervect]

The relationship that the velocity in the lab frame is 2*pi*r* revolutions / second, where r is the radius in the lab frame, doesn't change in the lab frame. The circumference of the disk in its own "frame" (which is not really a frame!) is different (larger) than 2*pi*r however. See any of the threads about the Ehrenfest paradox.

 

[QuantumHop]

The relationship that the velocity in the lab frame is 2*pi*r* revolutions / second, where r is the radius in the lab frame, doesn't change in the lab frame. The circumference of the disk in its own "frame" (which is not really a frame!) is different (larger) than 2*pi*r however. See any of the threads about the Ehrenfest paradox.

I thought something strange was going to happen but wasn't sure, thanks for the info.

I found this link, http://en.wikipedia.org/wiki/Ehrenfest_paradox

But I can't follow most of the math, why are they complicating things by using radius * pi? If I know the circumference I don't need pi. A circumference of 1m means it can rotate 299792458 times a second.

 

[QuantumHop]

Oh wait I think I see why they don't use its circumference.