1. The problem statement, all variables and given/known data A flywheel has shape as a homogeneous cylinder with mass m = 40,0 kg and radius r = 0,50 meters. The cylinder is rotating round the axis of symmetry, and is runned by a motor with constant angular velocity (w0). When the motor is switched off, the cylinder is affected by a moment of force that are caused by friction. How long will the cylinder rotate before the angular velocity is halved? 2. Relevant equations The friction: M = -kw w = omega k = (1,2 * 10^2) Nm/s 3. The attempt at a solution The moment of inertia: I = (m*r^2)/2 (cylinder) M = -kw => 1) w = -(M/k) w = 1/2*w0 alpha = w/T = (1/2*w0)/T 1) (1/2*w0) = -(M/k) (1/2*w0) = -((I*alpha)/k) (1/2*w0) = -((((m*r^2)/2)*((1/2*w0)/T))/k) When solving this equation the answer is: T = -416 BUT sadly we are quite sure this answer is incorrect, any help will be appreciated.