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Friction and angles

  1. Nov 19, 2014 #1
    how do you find friction force when applied force is at an angle, this is on a flat horizontal surface.
  2. jcsd
  3. Nov 19, 2014 #2


    Staff: Mentor

    Usually you will need to break at least one force into components.
  4. Nov 20, 2014 #3
    the static frictional force is :


    [Us] is constant and [F_n] is the wieght of the object the force is applied to plus the vertical component of the force ,, I think :)

    Remember that the frictional force is always in opposite direction of the applied force , that means they would have a different signs
    Last edited: Nov 20, 2014
  5. Nov 20, 2014 #4


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    Science Advisor
    Homework Helper
    Gold Member

    Fn is the force normal to the surface (it need not be the "weight" of the object or even "vertical").

    In these two examples the normal force is the weight of the object modified by the vertical component of the applied force F.

    in a) that would be

    Fn = mg+FSin(25)

    in b) that would be

    Fn = mg-FSin(25)

    Since friction is proportional to Fn that means b is easier than a)
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