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Homework Help: What fraction of the engine power is being used for the place to fly

  1. Nov 12, 2008 #1
    1. The problem statement, all variables and given/known data
    When its engine of power 76 kW is generating full power, a small single-engine airplane with mass 660 kg gains altitude at a rate of 2.8 m/s.
    What fraction of the engine power is being used to make the airplane climb?

    2. Relevant equations
    total power=76x10^3 W
    mass=660 kg
    dx/dt=velocity=2.8 m/s

    Power=mass x velocity

    3. The attempt at a solution
    (660x2.8)/(76x10^3) x 100 = 2.4% but this is wrong and im not sure where ive gone wrong
     
  2. jcsd
  3. Nov 12, 2008 #2

    LowlyPion

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    Re: Power

    There's no gravity?
     
  4. Nov 12, 2008 #3
    Re: Power

    oh of course

    660(2.8+9.8)/(76x10^3) x 100 =10.9%

    is that it?
     
  5. Nov 12, 2008 #4

    LowlyPion

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    Re: Power

    No. Because Power is Work / time = Force * distance / time

    In this case it is P = m*g *v
     
  6. Nov 12, 2008 #5
    Re: Power

    OK i get what you mean

    so its:

    660x2.8x9.8 / 76x10^3 x 100 = 23.8

    thank you lots
     
  7. Nov 12, 2008 #6

    LowlyPion

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    Re: Power

    There you go.

    Cheers.
     
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