physics

As a result of doing work a person supplies a machine with 1100 J of energy in 12 seconds. The machine in turn does work and delivers 900 J of energy in 14 seconds to some object. what is the effiecency of this machine?

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asked by CB
  1. Efficiency = Power out/ Power in
    = (900/14) / (1100/12)
    = 70%

    This assumes that the power is delivered continously and the stated measurements are typical of the average power in and out.

    If the work were done only during a 12 second interval and then recovered or "delivered" more slowly in a following 14 sec period, the efficiency would be (work out/(work in) = 900/1100 = 81.8%

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    posted by drwls

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