0
$\begingroup$
  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?
Improve this question
$\endgroup$
5
  • 1
    $\begingroup$ You may want to check out en.wikipedia.org/wiki/Ehrenfest_paradox $\endgroup$
    – nahano
    Commented Dec 5, 2014 at 7:32
  • $\begingroup$ @dacodemonkey and Key, this related answer of mine gives a short calculation demonstrating the problem that Ehrenfest highlighted. $\endgroup$
    – Danu
    Commented Dec 5, 2014 at 8:35
  • $\begingroup$ 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. $\endgroup$
    – Carl Witthoft
    Commented Dec 5, 2014 at 13:08
  • $\begingroup$ 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. $\endgroup$
    – mmesser314
    Commented Dec 5, 2014 at 14:32
  • $\begingroup$ Related: physics.stackexchange.com/q/8659/2451 and links therein. $\endgroup$
    – Qmechanic ♦
    Commented Jun 19, 2016 at 7:48

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.