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Homework Help: Finding theta when moment is max

  1. Oct 14, 2015 #1
    1. The problem statement, all variables and given/known data
    to achieve max moment , the 4 kN must br perpendiclar to 20m , right ? so, i formed a cloased triangle and use sine rule to find the
    tetha , 25/ sin90 = 4/sin tetha , i gt my tetha = 9.2 degree , but the ans given is 33.6degree
    i gt max moment = 80Nm

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Oct 14, 2015 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    You've applied the law of sines incorrectly to this problem. You can't measure the length of one side of a triangle in units of Newtons, and another in units of meters.
  4. Oct 14, 2015 #3


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    Education Advisor
    Gold Member

    And don't forget that the pivot point is shown as 1.5 m above the ground.
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