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Homework Help: Equilibrium of three suspended blocks

  1. Jan 20, 2012 #1
    1. The problem statement, all variables and given/known data


    The problem(s) are shown in the link, but I'm having trouble getting them started.

    2. Relevant equations

    3. The attempt at a solution

    For 3-12:

    I think what I need to do is find the tension force in the ropes leading from each block to point A. Then with those forces I find the Sum of the forces in X and Y

    From there i think i know what to do, its just that i dont know how to find the force in each rope!

    My attempt:

    For block B, the force in the the rope to point A is sin∅/200lb. For block C, the force in the rope to point a is sin(30)/100 =50lb .

    Is this correct so far?
  2. jcsd
  3. Jan 20, 2012 #2

    Doc Al

    User Avatar

    Staff: Mentor

    No. First things first. What's the tension in the rope connecting to B and the rope connecting to C? Hint: No calculation is required. (Consider the forces on B and C.) Then you can worry about the force components acting on point A.

    Careful how you write things: don't confuse sin(30)/100 with 100*sin(30).
  4. Jan 20, 2012 #3
    I got it figured out, I was definately over thinking it.

    The tension in the ropes are equal to the weight of the blocks, so rope AB is 200lb and AC is 100lb.

    Then I find the Sum of forces for X and Y and solve for the unknowns!

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