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Homework Help: Average power

  1. Oct 12, 2008 #1
    Hi guys i have a question on power and work i guess you gone help me out here is the question.

    1.A 1170 kg car starts from rest and accelerates uniformly to 10 m/s in 16.1 s . Assume that air resistance remains constant at 302 N during this time.Find the average power developed by the engine. Answer in units of hp.

    here is what i did

    Power = work / time
    so average power = KE/t

    work = 1/2 . mv^2
    work= 1/2 * 1170 * 10^2
    = 29250 J

    so Power = W/t = 29250 J/ 16.1
    = 3633.5403 w
    after that i changed watt to hp.
  2. jcsd
  3. Oct 12, 2008 #2


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    Science Advisor
    Homework Helper
    Gold Member

    Ok, good... you calculated the average power to accelerate the vehicle. But what about the work done to overcome drag? You have a nice constant 302N drag over this time. If you have force over a distance you can find work. Can you determine the distance the car went? Once you have work done by the air on the vehicle, divide by time to find average power.
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