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Homework Help: Forces involving static friction

  1. Sep 22, 2007 #1
    1. The problem statement, all variables and given/known data
    The floor of a railroad flatcar is loaded with loose crates having a coefficient of static friction of 0.25 with the floor. If the train is initially moving at a speed of 48 km/h, in how short a distance can the train be stopped at constant acceleration without causing the crates to slide over the floor?


    2. Relevant equations
    f = [tex]\mu[/tex] F
    F = m a


    3. The attempt at a solution
    This is my first post so I hope did it correctly. Ok so I first tried to draw a force diagram but this is the first problem that has included a speed into it. I know its probably something simple that I'm just not thinking of but I'm having trouble seeing how I can relate speed to any of the equations in this section. Thanks in advance.
     
  2. jcsd
  3. Sep 22, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    The speed will come in when you apply kinematics to find the shortest distance. But first you must find the maximum acceleration.

    Hint: What force accelerates the boxes? What's the maximum value of acceleration that that force can produce?
     
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