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Please help me tension/friction problem

  1. Oct 11, 2009 #1
    1. The problem statement, all variables and given/known data
    A 5.4 kg box is on a frictionless 44^\circ slope and is connected via a massless string over a massless, frictionless pulley to a hanging 1.4 kg weight.
    What is the tension in the string once the box begins to move?




    2. Relevant equations
    Fnet=ma


    3. The attempt at a solution
    I attempted to answer this using: w1= weight force of 5.4kg
    w2+ weight force of 1.4kg and T= tension exerted on string by each of the masses, mass 1=5.4kg and mass2=1.4kg

    So I have:
    T-w1*sin(44) = m1a1
    T-w2=m2a2
    a1=(m1/m2) a2

    but this gives me the wrong answer what am i doing wrong?
     
  2. jcsd
  3. Oct 11, 2009 #2

    rl.bhat

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    Homework Helper

    Hi juliadufosse, welcome to PF.
    In your attempt the first equation is correct.
    In the second equation, since mass is going down, it should be
    w2 - T = m2a2.
     
  4. Oct 11, 2009 #3
    if mass is going down shouldn't weight be negative and T-w2=m2a2
     
  5. Oct 11, 2009 #4

    rl.bhat

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    Then a2 should also be negative, because both of them are in the same direction.
     
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