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Homework Help: Coefficient of Kinetic friction and Friction force help! Thanks

  1. Nov 19, 2011 #1
    1. The problem statement, all variables and given/known data

    Im working on some typical "Ramp being pulled up an incline" questions and have trouble understanding something.

    An example question where it stats a box is being pulled up a ramp like the image below:

    Image: http://i43.tinypic.com/jb486q.jpg

    Now, first: In order to find the friction force exerted on the box.

    Would I simply just apply this: Δk - ΔUgravity / distance ?

    AND...To find the coefficient of Kinetic friction, do I just go:

    First find the normal force? which would be: n -mg cos 30 = 0, solve for n, which is 42.2N

    THEN, just use this formula? ; fk = µk n ?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Nov 19, 2011 #2


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    Homework Helper

    Isn't n = mg cos(30) ?
    Yes, Ff = µk*n and Ff = Δk - ΔUgravity / distance
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