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Homework Help: Power, Energy Problem

  1. Jan 12, 2012 #1

    k0k

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    A 1250-kg race car accelerates uniformly from rest to 30.0m/s in 4.00s on a horizontal surface with no friction. What must be the average power output of its motor? (Ans:141kW)

    --
    P=E/t
    F=ma
    Ek=1/2mv^2

    --

    P=E/t
    P=Ek/t
    =(.5X1250kgX15.0m/s^2) / (4.00s)
    =35156.25 W

    How exactly do I start this off? I assume that the change in energy should be kinetic only, right?.
     
  2. jcsd
  3. Jan 12, 2012 #2

    OmCheeto

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    Gold Member

    I think you would have had the correct answer had you not replaced the given 30 m/s with 15 m/s.
     
  4. Jan 12, 2012 #3

    k0k

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    OH, okay got it now. : D
    Thanks
     
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