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Homework Help: Cable tension statics problem

  1. Nov 14, 2004 #1
    1.) A uniform rod AB is 1.2 m long and weighs 16 N. It is suspended by vertical strings AC and BD. A block P weighing 96 N is attached at E, .3 m from A. The tension in the string BD is?
    I did:

    (.3m)(96N)+ (.9m)(16N) - (1.2 m)(x) = 0

    But the answer is 32 N

    What did I do wrong??

    2.) A 960 N block is suspended as shown. The beam is weightless and is hinged to the watt at A. The tensions in the cable BC is?

    I did:


    The answer is 1600 N.

  2. jcsd
  3. Nov 14, 2004 #2


    User Avatar
    Homework Helper

    In your first answer, you got the arithmetic wrong - I used the same pivot point you did and got 32N.

    In your second, you need to do a little trigonometry. The vertical component of the tension is 960N. Figure out what the total tension needs to be to get a vertical component of that magnitude. (Hint: you can get the angle at B with an Arctangent function.)
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