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Help with question related to friction on an incline?

  1. Oct 11, 2010 #1
    1. The problem statement, all variables and given/known data

    A car with a mass of 560 kg is parked on a hill inclined at 4.5 degrees to the horizontal.

    a.) What is the force of fricton necessary to hold the car on the slope?

    b.) If there is ice on the hill and the car is about to slip, what is the coefficient of static friction?

    2. Relevant equations

    Ff = u x Fn = u x mg(costheta)

    3. The attempt at a solution

    The answer I got for part a

    a =
    0 = - (9.8sin4.5 + U9.8cos4.5)
    u = 0.078
    Ff = (0.078)(560)(9.8)(cos4.5) Ff = 427N


    I'm stuck on Part B

    Thanks.
     
  2. jcsd
  3. Oct 11, 2010 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    hi pokeefer! :smile:
    it's just asking for the relation between friction force and the coefficient of friction :wink:
     
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