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Homework Help: Finding Friction force impeding boxs motion

  1. Nov 1, 2009 #1
    A 21.0 kg box is released on a 36.0° incline and accelerates down the incline at 0.271 m/s2. Find the friction force impeding its motion.



    I'm not sure what I'm doing wrong. Please help
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Nov 1, 2009 #2


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    the component of the weight acts downwards and the friction acts upwards (directions are parallel to the plane)

    so if the box moves down then ma=forces down-forces up.

    a bit easier now?
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