Relativistic Rotational Speed?

## Question:

What is the highest rotational speed ever achieved? If a theoretical
substance had infinite strength and was molded into a fly wheel, say with a
.5 meter radius, could the angular motion in theory approach the speed of
light, if given enough rpm?
Such a disk would be magnetically suspended in a vacuum using a linear motor
to provide the angular acceleration.
## Answer:

The fastest rotational speed I am aware of is a few hundred thousand rpm in
devices designed to store energy in the form of rotational inertia.
Theoretically there is no upper limit on the amount of energy stored in a
rotating object. As the tangential speed increases the relativistic mass
will increase increasing the moment of inertia so that any further increase
in speed requires incrementally more energy. The difficulty of course is in
the strength of the material. The force resulting from the centripetal
acceleration goes up as the rotational speed increases. Real objects fly
apart at velocities well below those where relativistic effects become
noticeable.
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