Need help finding coefficient of kinetic friction

  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. rock.freak667

    rock.freak667 6,220
    Homework Helper

    Constant speed means the resultant force is zero....so what is the value of the frictional force?
     
  4. 150 N. So the coefficient of kinetic friction would then be .38, correct?
     
  5. rock.freak667

    rock.freak667 6,220
    Homework Helper

    Yes that should be correct.
     
  6. Thanks!
     
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