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Homework Help: Thermal efficiency

  1. Dec 1, 2008 #1
    1. The problem statement, all variables and given/known data
    The power output of a car engine running at 1900 is 600 kilowatts per hour.
    How much work is done per cycle if the engine's thermal efficiency is 30.0 percent

    2. Relevant equations

    thermal efficiency=w(out)/Q(hot)

    3. The attempt at a solution
    It wants the answer in KJ/s so i converted the kilowatts to KJ/sec then divided by rev/s then multiplied by .3. What am i doing wrong? Any help would be appreciated.
  2. jcsd
  3. Dec 2, 2008 #2
    Looks like you should be multiplying by 10/3.
    The 600 kw/hr seems to be the power output after 70% of the initial energy has been lost.
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