Let's say we have two rotating disks and one disk is given some angular velocity. As one disk rotates, due to friction the other disk should rotate as well. The two disks are completely identical (radii, mass etc). The two disks are lined up next to each other horizontally, and only the rims of the two disks are in contact.
In this setup, the normal force and the frictional force are the most important forces. But what is the exact relation between the forces and how can we calculate them?