2–64.In a certain machine, the effortmoves 20 feet for every foot thatthe resistance moves.If themachine is 75 percent efficient,the force required to overcome aresistance of 300 pounds is1.15 lb2.20 lb3.25 lb4.30 lb2–65.If a block and tackle has atheoretical mechanical advantage of5 and an efficiency of 60 percent,the amount of force necessary tolift a 1,200–pound load is1.30 lb2.150 lb3.400 lb4.720 lb2–66.Which of the following statementsconcerning the relationship of workoutput and work input of a machineis correct?1.The output is the same as theinput2.The output is greater than theinput3.The output is less than theinput4.The output has no relationshipto the input2-67.The amount of work done divided bythe time required is called1.energy2.resistance3.force4.powerWhen answering questions 2–68othrough 2–73, assume 100 percentefficiency in each situation and use theappropriate power formula to calculate theunknown quantity.2–68.A motor–driven hoist lifts a165–pound load to a height of 50feet in 30 seconds.How much powerdoes the motor develop?1.1/4 hp2.1/2 hp3.3 hp4.10 hp2–69.A power winch is capable of liftinga 440-pound load a distance of 5feet in 1 second.The drivingmotor works at the rate of1.1/2 hp2.1 hp3.2 hp4.4 hp2–70.What is the horsepower of theengine driving the pump that lifts9,900,000 pounds of water per dayfrom a lake to the top of astandpipe,a vertical distance of120 feet? The engine runs at auniform speed 12 hours a day.1.12 hp2.15 hp3.24 hp4.50 hp2–71.While a propeller–driven aircrafttravels at a speed of 120 mph, itsengine develops 1,500 hp.Approximately what force in poundsis being exerted by the propeller?1.850 lb2.5,000 lb3.15,000 lb4.30,000 lb2–72.What is the horsepower of ahoisting engine that can raise6,000 pounds through a height of 44feet in one minute?1.3 hp2.4 hp3.8 hp4.12 hp20

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