210 Illustrative Problem # 2: Using the wheel and axle machine, a load of 1000 lb. can be raised by a force of 250 1b. applied to the rim of wheel. The radii of the wheel and axle are 50 inches and 10 inches respectively. Determine the AMA, IMA, and efficiency. AMA = Fout / Fin = 1000 lb / 250 lb = 4 IMA = Sin / Sout = 50 in / 10 in = 5 Efficiency = AMA / IMA = 4/5 x 100% = 80% Illustrative Problem # 3: In Figure 9.9-c, IMA equals 5. Assume that the output load is 3750 N and due to friction, efficiency is 75%. Find the applied load Fin. Efficiency = AMA / IMA, AMA = Efficiency x IMA AMA = 0.75 x 5 = 3.75 AMA = Fout / Fin- Fin = Fout / AMA = 3750 N / 3.75 Fin = 1000 N