1. The problem statement, all variables and given/known data I have a magnetic ball with magnetization M, mass m and radius R that starts to fall from rest through conducting tube of radius a little big larger than R, thickness [itex]\Delta[/itex] and conductivity [itex]\sigma[/itex]. The ball is not rotating, it said that magnetization is oriented vertically down. 2. Relevant equations Professor send me this problem, usually I know how to solve the problems that he sends me, but his one I don't know even how to start.