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Homework Help: Work and work of friction

  1. Oct 10, 2013 #1
    1. The problem statement, all variables and given/known data

    A box of mass 45 kg is initially at rest on a flat floor. The coefficient of kinetic friction between the box and the floor is 0.60. A woman pushes horizontally against the box with a force of 539 N until the box attains a speed of 2 m/s.

    What is the CM-work done by the friction force on the box?

    What is the work done by the woman on the box?

    2. Relevant equations

    W= F (Δ x)

    3. The attempt at a solution

    I tried solving for delta x by using force and mass to calculate for acceleration and then acceleration, Vo and Vf to find d (which I thought was Δ x) with the equation vf^2 = vo^2 + 2(a) d but I got the wrong answer
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 11, 2013 #2


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    Homework Helper

    You should get in the habit of drawing a free body diagram. They can basically solve the entire problem for you most of the time.

    If you do that, you will notice there are multiple forces at work here!
  4. Oct 11, 2013 #3
    This. Free body diagrams are the best thing that ever happened to intro mechanics.
  5. Oct 11, 2013 #4
    Always show your work so we can tell you where it went wrong.
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