# Frictionless cylindrical flywheel, of diameter 250mm and mass 30k

 Sci Advisor P: 1,498 The radius of gyration should be easy, it's just a simple formula. It's just a function of mass and moment of inertia if I remember correctly. OK, I looked it up, it's just: $$R = \sqrt{\frac{I}{m}}$$ As for the problem let's try and walk through it. From the mass, you will need to convert the equivalent moment that the mass is exerting on the flywheel. From there, you can plug it into the equivalent rotational f=ma equation: $$T = I\omega$$ With your moment of inertia and torque/moment, you can get a rotational acceleration. Your mass is 1.5m above the floor, so convert that to radians, and see how long it takes to hit the floor (from the rotational acceleration). Given rotational acceleration and time, you can now get your final rotational velocity and the kinetic energy which is the equivalent: $$KE = \frac{1}{2}I\omega^2$$ Good luck