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Help with summing the moments in statics

  1. Dec 15, 2016 #1
    1. The problem statement, all variables and given/known data
    I need to sum the moments on a and b but when i sum them at b the number I get doesn't work when I check and sum them at a.

    2. Relevant equations


    3. The attempt at a solution
     

    Attached Files:

  2. jcsd
  3. Dec 15, 2016 #2
    (-200x4)+(-60x2.5)+(-60x2.5)+(rbhx10)=rbh=110

    (200x6)+(-60x2.5)+(-60x2.5)+(rahx10)=-90

    Sum horz=0=110+200+rah if moments summed at A
    Rah=-310

    Sum horz=0=-90+200+rbh if moments summed at B
    Rbh=-110

    Why are they not the same I don't understand
     
  4. Dec 15, 2016 #3

    NascentOxygen

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    Staff: Mentor

    Should be rah
     
  5. Dec 15, 2016 #4

    NascentOxygen

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    Staff: Mentor

    The sum of the horizontal forces must be the sum of ALL horizontal forces. There are 3 forces with horizontal components. This sum equals zero and has nothing to do with the point about which you choose to sum moments.

    Another forces equation can be obtained by setting the sum of ALL vertical forces = 0
     
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