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Heat engines

  1. Dec 12, 2011 #1
    1. The problem statement, all variables and given/known data
    A certain engine can propel a 1600 kg car from rest to a speed of 22 m/s in 9.7 s with an efficiency of 23%.

    what is the rate of heat flow into the engine at the high temperature?

    what is the rate of heat flow out of the engine at the low temperature?

    2. Relevant equations

    e= 1- (Qout/ Qin)

    3. The attempt at a solution

    for the heat flow into the engine (high temp):
    K= 0.5mv^2= (0.5)(1600)(22^2)= 387200 J

    then I did 387200 J/ (0.23 x 9.7)= 199587.6289 J/s (not sure if this is correct)

    I'm unsure as to how to do the second part of the question. Please help!!! Thanks :)
     
  2. jcsd
  3. Dec 12, 2011 #2

    rock.freak667

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    Homework Helper

    Right so you have heat going in and work being done and heat going out.

    So by conservation of energy what equation must relate these quantities??
     
  4. Dec 12, 2011 #3
    I get it! thanks for your help :)
     
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