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Homework Help: Kinetic Friction and Newtons 2nd Law

  1. Mar 19, 2010 #1
    1. The problem statement, all variables and given/known data
    A car weighing 15000N experiences a drag force of 1200N. The car travels 30m/s on a level highway. The coefficient of kinetic friction is 0.2. If the car travels for 10s at this speed, calculate the power the engine produces.

    The car then goes up a 10 degree constant incline. Calculate the additional force the engine must now provide. Find the power for friction on the incline.


    2. Relevant equations
    F = ma
    MkFn
    a= v/t


    3. The attempt at a solution
    so far i got that 15000= mg m = 1529.1
    a = 3m/s^2
     
  2. jcsd
  3. Mar 19, 2010 #2

    PhanthomJay

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    I find the wording of this problem bothersome, since there is no kinetic friction involved unless the non-driving wheels are locked and skidding (the driving wheels are what propels the car forward, due to static friction, which does no work). Beyond that , the car is NOT accelerating...it is moving at constant speed. The driving force on the level surface is just the force necessary to overcome drag...and whatever kinetic friction force may be acting, if the non-driving wheels are locked.
     
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