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Homework Help: Pre-lab questions

  1. Mar 23, 2005 #1
    Hey guys any help on this question would be much appreciated

    A 700kg car accelerates from rest under constant power at t = 0. At t = 9s it is 117.7m from its starting position and its acceleration is then 1.09m/s2. Find the power, expended by the car's engine, neglecting frictional losses.
  2. jcsd
  3. Mar 23, 2005 #2
    Power = Work / Time
    Work = Force x Distance
    Force = Mass x Acceleration

    Power = Mass x Acceleration x Distance / Time
  4. Mar 23, 2005 #3
    I thought of that, but below that it says

    Hint: Start with the relationship between Power and Force, rearrange differentials to intergrate

    This just confused me, and I thought maybe it wasn't that simple as what you posted above
  5. Mar 23, 2005 #4
    All the integration will lead to the answer I gave you above.

    But in that case:

    [tex] dW = P dt[/tex]

    [tex] dW = F dx[/tex]

    [tex] P dt = F dx [/tex]

    Integrating both sides:

    [tex] \int { P dt } = \int { F dx } [/tex]

    [tex] Pt = Fx [/tex]

    [tex] P = \frac{Fx}{t} [/tex]

    Thats as differential as I can get.
  6. Mar 23, 2005 #5
    Ok thanks very much for your help
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