Need help finding coefficient of kinetic friction

  1. Jul 23, 2008 #1
    1. The problem statement, all variables and given/known data
    A horizontal force of 150 N is used to push a 40.0 kg packing crate a distance of 6.00 m on a rough horizontal surface. If the crate moves at constant speed, find the coefficient of kinetic friction between the crate and the surface.


    2. Relevant equations
    fK= coeff. of kin. friction X N
    Fy= -mgy + normal force


    3. The attempt at a solution
    I started by using Fy= -mgy + N to be 0= -40 (9.8) (cos 0) + N and found N be 392. But now I'm not sure where to go from here to find the coefficient of kinetic friction. Can anyone help?
     
  2. jcsd
  3. Jul 23, 2008 #2

    rock.freak667

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    Constant speed means the resultant force is zero....so what is the value of the frictional force?
     
  4. Jul 23, 2008 #3
    150 N. So the coefficient of kinetic friction would then be .38, correct?
     
  5. Jul 23, 2008 #4

    rock.freak667

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    Yes that should be correct.
     
  6. Jul 23, 2008 #5
    Thanks!
     
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