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Homework Help: Power, work and speed

  1. Nov 4, 2007 #1
    1. The problem statement, all variables and given/known data
    Car, mass 1000kg, accelerates from rest in straight line using constant mechanical power of 60kW.
    What is speed and acceleration after 5s.

    2. Relevant equations
    W = Kf - Ki
    P= dE/dt

    3. The attempt at a solution

    I've already worked out that the speed will be 24.5m/s. What I'm really wondering is if a constant mechanical power results in a constant acceleration. Any help would be appreciated. Thanks.
  2. jcsd
  3. Nov 4, 2007 #2
    I attempted to do the following:

    F = ma, but F is provided by the motor. Therefore, P = Fv
    60 000W = 24.5 x F
    F = 2450 N

    2450N = 1000kg x a
    a = 2.45m/s^2

    Does this seem like a reasonable approach?
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