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Angles and Calculations

  1. Feb 19, 2015 #1
    1. The problem statement, all variables and given/known data
    A vertical post is held in place by two cables as shown.

    2. Relevant equations
    SOH CAH TOA

    3. The attempt at a solution
    http://postimg.org/image/6rgssb1j5/

    The answer in the textbook is 63 degrees. Is this an issue or did I do something terribly wrong?
     
  2. jcsd
  3. Feb 19, 2015 #2

    ehild

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    The tension in the cables keep the post in vertical position. Its top point can not move sideways, the horizontal components of the tensions balance each other.
    The vertical components do not need to be equal, as they are balanced by the force from the ground.
     
  4. Feb 19, 2015 #3
    Unfortunately, I do not fully comprehend this explanation. My question is why 33 degrees is not the correct angle for Theta.
     
  5. Feb 19, 2015 #4

    ehild

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    You calculated theta from the condition that the vertical components of the tensions are equal, which is wrong .
     
  6. Feb 19, 2015 #5
    I believe I understand this comment now.

    Overview:
    To keep the vertical post upright, both the left and right side of the ground by the tensional strings will be equal to each other.

    1500cos50 = 964.1814 N = Adjacent Side (floor)
    Cos Inv. (964.1814/2100) = 62.6688 N (angle required to keep the pole upright)
     
  7. Feb 19, 2015 #6

    ehild

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    And the rounded value is 63°.
     
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