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  1. I was wondering the problems that would occur (aside from mechanical friction), when a disc rotates at high angular velocity. Is centripetal force an issue if high torque is applied on a disc (massive forces in the range of $100kN$ or $1MN$)?

Of course with the supply of high energy, just wanted to understand the problems that could occur when a disc rotates quite fast due to high torque.

  1. Also, at what speed is a disc considered moving near the speed of light?
Qmechanic
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    You may want to check out http://en.wikipedia.org/wiki/Ehrenfest_paradox – nahano Dec 05 '14 at 07:32
  • @dacodemonkey and Key, this related answer of mine gives a short calculation demonstrating the problem that Ehrenfest highlighted. – Danu Dec 05 '14 at 08:35
  • Quite a lot of careful materials engineering goes into disk brake design for ultra-high-speed vehicles precisely because of the centripetal force levels. It isn't just torque (acceleration) but the energy of the rotating material itself. – Carl Witthoft Dec 05 '14 at 13:08
  • A disc is moving near the speed of light when relativistic effects become important. This depends on how sensitive your measurements are. For example, the fractional change in circumference is $sqrt(1-v^2/c^2)$. For a bicycle wheel 1m in diameter and spinning at 3 m/s, this is about 10nm. If that much change is important, the bicycle wheel is relativistic. – mmesser314 Dec 05 '14 at 14:32
  • Related: http://physics.stackexchange.com/q/8659/2451 and links therein. – Qmechanic Jun 19 '16 at 07:48

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