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Help Please: Cable Tension Problem

  1. Aug 21, 2006 #1
    I can't figure this out for the life of me :yuck: .

    A large, 2000 pound block is being held by two ropes that were attached to a horizontal beam. The rope on the left made a 30 degree angle, the rope on the right made a 40 degree angle (see image). What is the tension in the left cable?

    HINT: Round to the nearest whole number. Do not enter units.

  2. jcsd
  3. Aug 21, 2006 #2

    Doc Al

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    Staff: Mentor

    Start by labeling all the forces acting on the block. Hint: Since the block is in equilibrium, what can you say about the net force on it?
  4. Aug 22, 2006 #3


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    Homework Helper

    Maybe you should replace the block by a single black dot at the point of intersection of the ropes. What forces are the block experiencing from the ropes and in which directions are these forces? Can you think of any other forces acting on the block?
  5. Aug 22, 2006 #4
    1) Draw a free body diagram showing the tension forces in both strings: call them T1 and T2 if you want.
    2) Write down Newton's law -> Sum of forces = ma; since this object is in equilibrium though, sum of forces = 0.
    3) Resolve T1 and T2 into their respective x and y components, and then apply Newton's law to each component...
    e.g. T2X - T1X = 0 where T1X and T2X and the x-components of T1 and T2 respectively..
    Then you'll have two equations in two unknowns; use your knowledge of linear systems to solve for them and you'll be fine. :D
  6. Aug 22, 2006 #5


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    A Classic in Statics :!!) . Hehe 2 eqs, 2 unknowns.
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