... U Mobile 9:45 PM 52% 4 A multiple disc has radial width of the friction material 1/5th of the maximum radius. The coefficient of friction is 0.25. Find the total unmber of discs required to transmit 60 kW at 3000 r.p.m. The maximum diameter of the clutch is 250 mm and the axial force is limited to 600 N. Also find the mean unit pressure on each contact surface.