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Homework Help: Tension in a rope

  1. Nov 21, 2009 #1
    1. The problem statement, all variables and given/known data
    I have a 1 kg ball hanging from rope A, and a 2 kg ball connected to the 1 kg ball by rope B. They are accelerating up at 4.0 m/s^2. I need to know the tension in rope A and rope B.

    2. Relevant equations
    Tension = Fg + ma ?????

    3. The attempt at a solution
    Rope A: (1 kg + 2 kg) * (9.8 m/s^2) + (1 kg + 2 kg) * (4 m/s^2) = 41.4 N
    Rope B: (2 kg) * (9.8 m/s^2) + (2 kg) * (4 m/s^2) = 27.6 N

    Am I doing this correctly?
  2. jcsd
  3. Nov 21, 2009 #2
    I think since the ropes are accelerating in the vertical direction , the sum of all forces acting on the ropes with the attached ball will be equal to an accelerating force, not zero. Have you sketched a free body diagram of all the forces acting upon the two ropes? .
    Last edited: Nov 21, 2009
  4. Nov 21, 2009 #3


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    Looks good! :smile:

    p.s. Welcome to Physics Forums.
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