The flywheel of a punching machine has a mass of 300 kg and a radius of gyration of 600 mm. Each punching operation requires 2500 J of work. (a ) Knowing that the speed of the flywheel is 300 rpm just before a punching, determine the speed immediately after the punching. (b) If a constant 25-N.m couple is applied to the shaft of the flywheel, determine the number of revolutions executed before the speed is again 300 rpm.

3

A uniform 144-lb cube is attached to a uniform 136-lb circular shaft as shown, and a couple M with a constant magnitude is applied to the shaft when the system is at rest. Knowing that r = 4 in., L= 12 in., and the angular velocity of the system is 960 rpm after 4 s, determine the magnitude of the couple M.

16.25 The 160-mm-radius brake drum is attached to a larger flywheel that is not shown. The total mass moment of inertia of the drum and the fly- wheel is 18 kg m and the coefficient of kinetic friction between the drum and the brake shoe is 0.35. Knowing that the angular velocity of the flywheel is 360 rpm counterclockwise when a force P of magnitude 300 N is applied to the pedal C, determine the number of revolutions executed by the fly- wheel before it comes to rest. 16.26 Solve Prob. 16.25 assuming that the initial angular velocity of the flywheel is 360 rpm clockwise. 200 mm Fig. P16.25 120 min 160 mm 300 mm- D