A demonstration gyroscope consists of a uniform disk with a 39-cm radius, mounted at the midpoint of a light 56-cm axle. The axle is supported at one end while in a horizontal position. How fast is the gyroscope precessing, in units of rad/s, if the disk is spinning around the axle at 34 rev/s?

Answer 1

The equation you need can be found at
http://physics-animations.com/Physics/English/gyro_txt.htm

The mass will cancel out when you insert (1/2)M R^2 for the moment of inertia.
r in the reference above is the distance from the support point to the rotor. wp is the precession rate that you want

Answer 2

what radius should we use again?