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Homework Help: Sliding Box

  1. Feb 10, 2009 #1

    TG3

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    1. The problem statement, all variables and given/known data
    A box of unknown mass slides across a frictionless floor with an initial speed of 4.7 m/s. It encounters a rough region where the coefficient of friction is µk = 0.3
    Part 1:
    What is the shortest length of rough floor which will stop the box?
    Part 2:
    What is the shortest length of rough floor which will stop the box?

    2. Relevant equations

    vf^2 = vi^2 + 2a delta x.
    Frictional force = mew times the normal force

    3. The attempt at a solution
    Final velocity = 0, so
    0 = 4.7 ^2 + 2A delta x.
    A = the frictional force.
    How can I determine the normal force (and after that, the frictional force, and after that, the change in distance) if I don't know the weight of the box? Is there another way to do this problem?
     
  2. jcsd
  3. Feb 10, 2009 #2

    LowlyPion

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    Homework Helper

    F = ma = μ*m*g

    a = μ*g

    Does that help?
     
  4. Feb 10, 2009 #3

    TG3

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    Yes- it certainly does. With that I was able to solve both parts of the problem. I'm writing that formula down for future reference...
     
  5. Feb 10, 2009 #4

    LowlyPion

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    Better to understand it and remember it forever.
     
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