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Homework Help: Annoying Tension Problem

  1. Nov 26, 2007 #1
    1. The problem statement, all variables and given/known data

    A 168 N bird feeder is supported by three cables, as shown in Figure P4.17. Find the tension in each cable.

    picture can be found here: http://www.webassign.net/sf5/p4_13.gif

    2. Relevant equations

    all trig functions

    3. The attempt at a solution

    left cable:
    sin(60) = 168/T
    T = 336

    this did not work when i put in the answer on webassign so i didnt even try for the right cable

    I think i'm doing something fundamentally wrong.
  2. jcsd
  3. Nov 26, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    The vertical cable should be straightforward. It bears the entire weight of the bird house (including whatever bird(s) and food happen to be supported by it).

    The two diagonal cables have to be resolved into horizontal and vertical components.

    The horizontal components must be equal and opposite (i.e. one force is the opposite of the other).

    The sum of the vertical components must equal _________________?

    Please write the equations for the horizontal and vertical net forces for the diagonal cables.

    BTW, welcome to PhysicsForums!
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