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Homework Help: Statics - Pin & Slider Structure - Equilibrium

  1. Dec 27, 2013 #1
    1. The problem statement, all variables and given/known data


    Given force F (=5000N), find Moment on member 4.

    I have attempted to start solving this problem by drawing the following diagram:


    I added the letter 'A' to the support of member 2, and also put an angle of 7 degrees to the vertical at the support 1.

    I have drawn force and moment reactions on bodies 3, 5 and 8 which are all sliders and reaction forces on pins D, F, E, G and A.

    I worked out the geometry so as to be able to work out moments and components.

    2. Relevant equations

    To solve the problem I tried to use the Equilibrium equations which state that forces in all directions should equal to zero and also that all moments should equal to zero.

    3. The attempt at a solution

    Member 4:[tex] \sum{F_x} = 0: B\cos(15)+G_x-C\cos(7)=0
    \\ \sum{F_y}=0: B\sin(15)-C\sin(7)-G_y=0
    \\ \sum{M_G}=0: B(1.54) - C\cos(7)(6.4) -C\sin(7)(1.71) + M_3 = 0[/tex]

    Member 2:[tex]\sum{F_x}=0: A\sin(30) - B\cos(15) = 0
    \\ \sum{F_y}=0: A\cos(30) + B\sin(15) = 0
    \\ \sum{M_A}=0: B(0.8)=0[/tex]


    Equations of member 2 get me to a conclusion that member 2 is a zero force member. Am I right?
    Are my equations and diagram correct ?
  2. jcsd
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