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Question by lin: Efficiency of Machine? A pulley system is used to lift a piano 1.6 m. The acceleration of gravity is 9.81 m/s2 . If a force of 2426 N is applied to the rope as the rope is pulled in 20 m, what is the efficiency of the machine? Assume the mass of the piano is 668 kg. Answer in units of %. Best answer:
Answer by John
work = force * distance work needed to raise piano weighing 668kg through 1.6m against gravity 9.81m/s2 is 668 * 9.81*1.6 = 10485J work done on pulley system is 2426N * 20m = 48520J efficiency is 10485 / 48520 *100% = 21.6% (very low for pulley system)