text: sum of forces = m a\na is centripetal = v^2/r\nForce of Friction = ForceNormal times coeffiecint of friction\nForceNormal times coeffiecint of friction  = mv^2/r\nmg(coeffecient of friction) = mv^2/r\nmasses cancel out.\ngr(coeffecient of friction) = v^2\nv = sqrt[(coeffecient of friction)(gr)]\njust plug in for the coeffecient of friction.