A riveting machine is driven by a constant torque 4 kW motor. Each riveting operation takes 1 second and requires 900 N-m of energy. A flywheel of mass 130 kg and radius of gyration 0.5 m is fitted to the riveting machine. If the speed of the flywheel is 420 rpm before riveting, find
1 The fall in the speed of the flywheel after riveting.
2 The number of rivets fitted per hour.