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A Uniform Beam Supported by a Cable

  1. Jan 21, 2013 #1
    1. The problem statement, all variables and given/known data

    A uniform 250 kg beam is supported by a cable connected to the ceiling, as shown in the figure. The lower end of the beam rests on a rough, horizontal floor. What is the magnitude of the tension in this cable?

    Image of the problem:
    http://session.masteringphysics.com/problemAsset/1026378/6/yg.10.70.jpg

    2. Relevant equations

    Fnet=ma=0

    3. The attempt at a solution

    I know that this problem is easiest to complete using torques, but I was told to try it without using torque (if possible). That being said, here is my attempt:

    http://imgur.com/jKr3tDC

    I know that I got the right answer but I am not sure how. Aren't the 40 degrees and the 20 degrees are the wrong angles to use when using a horizontal/vertically oriented plane?
     
  2. jcsd
  3. Jan 21, 2013 #2

    haruspex

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    Your working does indeed look wrong.
    You show the tension resolving into T cos(20o) horizontally and T sin(20o) vertically, whereas the cable makes an angle 60o to the horizontal.
    You don't show any frictional force at the ground, but there must be one.
     
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