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Homework Help: Accelerating Car & Power

  1. Oct 10, 2005 #1
    A car of mass 880.0 kg accelerates away from an intersection on a horizontal road. When the car speed is 13.8 m/s, the net power which the engine supplies is 3700.0 W ( in addition to the extra power required to make up for air resistance and friction). Calculate the acceleration of the car at the time.

    I used the equation for power. P= change in work/ t
    3700= (1/2)mv^2 / t
    3700=83793.6 t
    I solved for t to get 22.7 s.
    I then used the equation for acceleration, change in v/ change in t
    a= 13.8-0/ 22.7-0
    and got the a to be .607 m/s^2
    This wasn't right.

    Can someone help me out? Thanks
  2. jcsd
  3. Oct 10, 2005 #2

    Physics Monkey

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    You have to use the differential form: [tex] P = \frac{dW}{dt} = F v [/tex]. So the power is the force times the velocity, can you now find the acceleration?
  4. Oct 10, 2005 #3
    Ok I got it.. thanks a lot!
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