Disk A, with a mass of 6.0kg and a radius of 30cm , rotates clockwise about a frictionless vertical axle at 10rev/s . Disk B, also 6.0kg but with a radius of 20cm , rotates counterclockwise about that same axle, but at a greater height than disk A, at 10 rev/s . Disk B slides down the axle until it lands on top of disk A, after which they rotate together.
A) After the collision, what is their common angular speed.