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Power required to move up an incline

  1. Mar 17, 2009 #1
    1. The problem statement, all variables and given/known data

    What power is needed to drive a car at 60 km/h up a 10% grade.

    mass=1800kg
    v=60km/h
    theta=5.7106
    g= 9.81 m/s^2

    2. Relevant equations

    P = Fv
    P_ave= W/T
    w=mg
    F=ma


    3. The attempt at a solution

    I drew my diagram and FBD.

    Since Fy=mAy=0..

    0=N-sin(5.7106)
    N=1755.2477

    I know that Ax will be 0 since the velocity is constant, and I need to find the frictional constant:

    mAx=0=F-uk-mgcos(5.7106)

    But I don't have F, since it's what I'm trying to find..and this is where I've been stuck.
     
  2. jcsd
  3. Mar 17, 2009 #2

    LowlyPion

    User Avatar
    Homework Helper

    Welcome to PF.

    Maybe consider the rate of change of potential energy?
     
  4. Mar 17, 2009 #3
    Problem with that is we haven't learned anything about energy yet so we are supposed to use regular Work, Power, and other Motion formulas.
     
  5. Mar 17, 2009 #4

    LowlyPion

    User Avatar
    Homework Helper

    OK. So consider then the force of gravity along the incline.

    The car travels at 16.667 m/s, so in 1 second, what force was required to overcome gravity over that distance?

    That gives you W per sec = F*d per sec.
     
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