[Ether]

@Ninja_Bait:

My apologies, I misunderstood your earlier post. I see you edited it. I had the original version still on the screen when I replied to it (got interrupted).

The net force acting on the motor+wheel assembly points directly to the pivot. This must be the case, since the angular acceleration is zero (the problem stated that the angular velocity is constant).

The net force is equal in magnitude to the tension minus the friction. Since these are the only two external forces acting on the motor+wheel assembly, the friction must be pointing directly away (radially) from the pivot.

As posted earlier, the magnitude of the friction force is simply mu_k*W (if we assume the Coulomb friction model).