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Multiparticle Systmes

  1. Mar 23, 2009 #1
    1. The problem statement, all variables and given/known data
    It is sometimes claimed that friction forces always slow an object down, but this is not true. If you place a box of mass M on a moving horizontal conveyor belt, the friction force of the belt acting on the bottom of the box speeds up the box. At first there is some slipping, until the speed of the box catches up to the speed v of the belt. The coefficient of friction between box and belt is . Do not worry about italics. For example, if a variable g is used in the question, just type g and for use mu.

    (a) What is the distance d (relative to the floor) that the box moves before reaching the final speed v? (Use energy arguments to find this answer.)

    (b) How much time does it take for the box to reach its final speed?


    2. Relevant equations
    W=-Fd/2
    K=1/2mv^2
    f=mu*N


    3. The attempt at a solution
    Can't figure it out.
     
  2. jcsd
  3. Mar 23, 2009 #2

    tiny-tim

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    Welcome to PF!

    Hi jchojnac! Welcome to PF! :smile:

    (have a mu: µ :wink:)
    Hint: for (a), use the work-energy theorem:

    work done by friction = energy gained :smile:
     
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