Information for questions 2–55 ando2–56:You want to raise an1,800–pound motor 4 feet up to afoundation.You use two double–sheaveblocks rigged to give a mechanicaladvantage of 4 and a windlass that has atheoretical mechanical advantage of 6.2–55.Assuming 100 percent efficiency,how much work is required to raisethe motor?1.1,800 ft-lb2.3,600 ft–lb3.7,200 ft–lb4.10,800 ft–lb2–56.Neglecting friction, how much pullmust you exert to raise the motor?1.18 lb2.36 lb3.75 lb4.300 lb2-57.An effect which friction has on themechanical advantage of any machineis to make the1.theoretical mechanicaladvantage less than the actualmechanical advantage2.actual mechanical advantageless than the theoreticalmechanical advantage3.actual mechanical advantageless than one4.actual mechanical advantagemore than one2–58.Assume that the hammer of a piledriver weighs 1,000 pounds. Theresistance of the earth is 6,000pounds.If the hammer drops 4 feetto drive a pile, how far into theearth will the pile be driven?(Assume an efficiency of 100%.)1.2 in2.6 in3.8 in4.10 inWhen answering questions 2–59othrough 2–61, assume that a manlifts a 600–pound load, using a block andtackle with a theoretical mechanicaladvantage of 6.He does 6,500 foot–poundsof work in lifting the load 8 feet.2-59.How much work does the man do inovercoming friction?1.215 ft–lb2.813 ft–lb3.1,700 ft-lb4.5,900 ft–lb2–60.The total force exerted by the manin lifting the load isapproximately1.35 lb2.135 lb3.215 lb4.406 lb2–61.The average amount of force whichthe man exerted to overcomefriction is approximately1.35 lb2.215 lb3.237 lb4.406 lb2–62.The handle of a screwjack must movethrough a circular distance of 600inches to lift a load one inch. Ifa force of 10 pounds is required tolift a load of 1,500 pounds, whatis the efficiency of the jack?1.25%2.33%3.78%4.90%2-63.A block and tackle has atheoretical mechanical advantage of4 but requires a force of 50 poundsto lift a 160–pound load.Theefficiency of the block and tackleis1.60%2.70%3.80%4.90%19

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