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Homework Help: Friction and Normal Force

  1. Oct 2, 2011 #1
    1. The problem statement, all variables and given/known data

    A pizza box thrown across the room strikes
    the floor with a horizontal velocity of 2.0 m/s.

    2. Relevant equations

    If the 300-g box encounters a floor with a
    coefficient of kinetic friction of 0.3, how far
    will the box slide before coming to rest?


    3. The attempt at a solution
    So I did it by using the equation a=ug(u is coefficient of kinetic friction), and I got -2.94 m/s^2 as the acceleration. Then, I used a kinematics equation and found d to be 0.68 m, but the answer says its 0.068 m. Is the answer at the back wrong?

    Also, I was wondering if the given 300g mass of the box was needed in the solution?
     
  2. jcsd
  3. Oct 2, 2011 #2

    PeterO

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    Homework Helper

    I like your answer, and you don't need the mass - unless you are unaware of the a = μg arrangement and want to do it from first principles..
     
  4. Oct 2, 2011 #3
    So my answer is right?
     
  5. Oct 2, 2011 #4

    PeterO

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    Homework Helper

    I think so. It would take 3g acceleration to slow from 2 m/s in only 0.068 m.
     
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