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Homework Help: Block on an incline with Friction

  1. Jul 15, 2009 #1
    1. The problem statement, all variables and given/known data

    A block with a mass of m = 2.29 kg is at rest on an incline. The angle of the incline is θ = 15.9° with respect to the horizontal. The coefficient of static friction between the object and the incline is μs = 0.579, the coefficient of kinetic friction is μk = 0.389.

    What would be the magnitude of the object's acceleration after an initial impulse set it in motion uphill on the incline?

    2. Relevant equations
    Newtons Second Law
    F= ma

    3. The attempt at a solution

    [-(coefficient k)mg-mgsin(theta)]/m and then making that answer positive because it is a magnitude. Where am I going wrong here?
  2. jcsd
  3. Jul 15, 2009 #2


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    Science Advisor
    Homework Helper

    You probably aren't actually drawing a force diagram. The frictional force is proportional to the normal force, which isn't mg. The normal force depends on the angle too.
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