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Homework Help: Atwood/Pulley Problem

  1. Jan 28, 2008 #1
    1. The problem statement, all variables and given/known data

    140 gram mass & a 110 g mass are connected by a masless string passin over a massles pully which has a frictional resist. f=0.147 N when M (total weight of 2 masses) = 250 g.

    -What's the acceleration of the system after release?
    -How far does the 140 g mass fall during a 1.5 s interval following release from rest
    -what's the minimum mass differnce for which the pulley syst. will have a non-0 acceler. when released from rest when M = 250 g

    2. Relevant equations

    Somethin like this?

    T1 + T2 = (m1 + m2)g + (m2-m1)a

    3. The attempt at a solution

    The third question's my problem. For the first one, I'm guessin it'd be right just to use the equation to solve for a and T1/T2 would be the weight of each mass multiplied by gravity's constant? Would you use kinetic equations once you find acceleration to find how far the mass would fall during 1.5 s?
  2. jcsd
  3. Jan 29, 2008 #2


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    Homework Helper

    If there were no friction the resultant force acting on the system would have been the difference between the weight of the larger mass and the smaller mass (the tensions would have been the same and cancelled each other out since they are opposing each other). With friction the resultant force is reduced according to the magnitude of the friction (that is the one tension is less than the other by the size of the friction).
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