13-20.The coefficient of kinetic friction for mass B in Figure P13-20 is 0.25. Determine the acceleration of mass A if it has a mass of (a) 30 kg and (b) 50 kg. A B 100 kg = .25 FIGURE P13-20 3 13-36.A 1000-kW generator has a 3500-lb rotor that is accelerated from rest to 3600 rpm in 10 seconds. Determine the torque required. Assume the rotor to be a solid cylinder 40 in. in diameter. 13-41.A 150-mm-diameter shaft with a mass of 20 kg is rotating at 900 rpm. A pulley mounted on the shaft has a mass moment of inertia of 0.15 kg. m. If the shaft and the pulley coast to a stop due to a tangential frictional force of 8 lb at the outer radius of the shaft, determine the time required.