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Friction stopping problem

  1. Feb 16, 2009 #1
    1. The problem statement, all variables and given/known data

    A crate is sitting on the back of a truck at 20 m/s with a μ of 0.4. With what acceleration can the truck stop without having the crate slide?

    2. Relevant equations

    I'm not sure if I am supposed to use this equation:

    a = μ(9.8)

    3. The attempt at a solution

    a = 0.4(9.8) = 3.92 m/s^2.
  2. jcsd
  3. Feb 16, 2009 #2
    That is correct, nice job.
  4. Feb 16, 2009 #3
    So is the 20 m/s not needed?
  5. Feb 17, 2009 #4
    That is correct. You are only asked for acceleration (or deceleration in this case), so initial velocity doesn't come into play.
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