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Homework Help: Accelerating car, kinematics problem

  1. Oct 20, 2008 #1
    A 2.3 103 kg car starts from rest and accelerates along a horizontal roadway to +17 m/s in 21 s. Assume that air resistance remains constant at -500 N during this time. Find
    (a) the average power developed by the engine and

    (b) the instantaneous power developed at t = 15 s.

    I am really confused about this. If you can help, I would appreciate it. Thanks!
     
  2. jcsd
  3. Oct 20, 2008 #2
    Re: Work/energy

    I find a good place to start on any problem is to list the knowns and unknowns, then find equations that deal with those properties/units.

    For instance, here you are given :
    mass
    initial velocity
    final velocity
    time
    a force acting on the system

    and you are looking for:
    power

    Keep in mind, power will have units in terms of Watts (or kW)
    Power = Work / time
    Work = Force * distance
    Force = mass * acceleration


    See if you can get started with that.
     
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