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Homework Help: Where Am I Going Wrong?

  1. Sep 14, 2007 #1
    1. The problem statement, all variables and given/known data

    In the simplest form of Atwood machine,two masses are 0.3 kg and 0.6 kg.We consider massless pulley,string and frictionless surfaces.we let the arrangement move at t=0.
    You can calculate that the tension in the string is 3.9 N and the acceleration~3.26

    The larger mass is stopped 2 seconds later the arrangement started moving.
    We are to find the timee elapsed before the string is taut again.
    2. Relevant equations
    3. The attempt at a solution

    I thought that the lighter mass would move upwards (at the instant bigger mass was stopped) with speed: v=at=(3.26x2) m/s=6.52 m/s

    Then using total time of flight I got T=(2v/g)=1.33 s

    Whereas the answer is 0.67 s

    can anyone show me if I am wrong?
  2. jcsd
  3. Sep 14, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    I don't think you're wrong--I agree with your answer.
  4. Sep 14, 2007 #3
    thank you
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