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Homework Help: Can anyone help me with an equilibrium problem?

  1. Dec 22, 2009 #1
    1. The problem statement, all variables and given/known data
    Basically, this is the problem,
    A 70 kg painter is painting the wall of a building. He stands on a horizontal board of length 6.4 m and mass 15 kg, suspended from vertical ropes attached to each end. If the painter stands 1.2 m from one end of the board, what would the tensions in the ropes be?

    2. Relevant equations
    I know that the sum of all forces in the x direction must add to zero, as well as the sum of the forces in the y direction.

    3. The attempt at a solution
    I tried to, using a coordinate system, account for the mass of the board, as well as the human, but i simply do not know how to calulate the Tension of the ropes, both the rope far away and the rope close to the man. I do know that the tension closer to the man would be greater. Any help please?
  2. jcsd
  3. Dec 22, 2009 #2


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    Welcome to Physics Forums.

    Can you show the equations you have set up for forces in the y direction?

    Also, you will need to consider torque to solve this problem.
  4. Dec 22, 2009 #3
    Try thinking of it this way. If tou were walking along a see saw starting at the center--it wouldnt take long before you tipped over. Now imagine you have people on each end pushing if needed to maintain equilibrium. Who has to push, and who should pull?

    Hint: Only one has to push. Tension is different--you cannot push, only pull. So any tendency to tip over has to be cancelled by the difference in pulls, the sum of the pulls must equal the overall weight.

    Edit: sorry redbelly, was working on mine, when yours was posted.
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