1. A solid disk of radius R and mass M is initially spinning clockwise with an angular velocity magnitude ω. It is placed against a flat, horizontal surface with a coefficient of kinetic friction of μ. Find the frictional torque magnitude on the disk, and how long it will take the disk to come to rest. 2. Relevant equations I know that for finding how long it will take to stop I need ω=ω0+αt and to find α I use T=Iα. However, I'm not sure how to find T for the first part. I also think that I might need the inertia of a disk, so that's I=½MR2 3. The attempt at a solution Alright so as I said I pretty much know how to find the time needed for it to come to a stop, however how in the world do I find the torque? All of my equations for finding torque involve F, like T=rFsinθ, but the problem has no F, is there a different equation I should be using or something? I had originally tried using the T=rFsinθ and had θ=90, and I made the Force be the Fk, but apparently that's wrong cause I got marked off for it. Please I need some clear guidance.