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Homework Help: Coefficient of friction problem

  1. Apr 28, 2012 #1
    Here is the problem:
    "A small package rests on the horizontal dashboard of a car. If μs = 0.333, what is the minimum acceleration of the car that will cause the package to slip off, assuming that the car is on a level road?"

    I really have no clue. Any equations I feel are relevant (μ =F/N,standard kinematics equations) require far more information than I have.

    Help please?
  2. jcsd
  3. Apr 28, 2012 #2
    Try drawing a free body diagram and looking at the forces that are involved 1st. There are probably several ways to look at it, but this essentially would boil down to a box on a moving ramp problem.
  4. Apr 28, 2012 #3
    Assume that the mass of the package is m, and the acceleration of the car is a.
    Assuming that the package doesn't slip, in terms of m and a (and g), what are the horizontal and vertical forces acting on the package?

    The package will slip only if the calculated horizontal force is greater or equal to the vertical force times the coefficient of static friction. (The mass should cancel out of your final equation.)
  5. Apr 28, 2012 #4
    Alright, I did this and found out ma = mgμ, and then subsequently solved it. Thanks.
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