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Homework Help: Car on Icy Hill

  1. Jan 28, 2007 #1
    1. The problem statement, all variables and given/known data
    On an icy day, you worry about parking your car in your driveway, which has an incline of 13°. Your neighbor Ralph’s
    driveway has an incline of 8°, and Bonnie’s driveway across the street has one of 5°. The coefficient of static friction
    between tire rubber and ice is 0.15. Which driveway(s) will be safe to park in?

    2. Relevant equations
    Force of friction=F*u

    3. The attempt at a solution
    How can we know 'F' without knowning the mass of car?
  2. jcsd
  3. Jan 28, 2007 #2


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    Staff Emeritus
    Science Advisor

    Just let mass=m, and leave it in the equations. When comparing the components of the forces in the horizontal direction, the masses will cancel.
  4. Jan 28, 2007 #3
    Here is what I just did...

    Sum of Forces in horz direction,
    Since F_f=u*F_n
    Divide by F_n, solve for @ to be 8.6 degrees. So both Ralph's and Bonnie's driveways will be ok?
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