Disk a, with a mass of 2.0kg and a radius of 80cm , rotates clockwise about a frictionless vertical axle at 20rev/s . disk b, also 2.0kg but with a radius of 30cm , rotates counterclockwise about that same axle, but at a greater height than disk a, at 20rev/s . disk b slides down the axle until it lands on top of disk a, after which they rotate together. part a after collision, what is their common angular speed (in rev/s)? part b and in which direction do they rotate? a) clockwise b) counterclockwise