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Statics Help: Support Reactions

  1. Apr 12, 2007 #1
    Please click on the image to make it larger.

    [​IMG]
    I understand the problem here, what I don't see is how to find the support reactions. Since at each joint we have more than two unknowns I have to find the support reactions. I have the answer to the problem. Could someone tell me how to find the support reactions? It seems like I need to take the moments about G and or F to get the support reactions at the pin at A and the rocker at E. Is this true?
     
    Last edited: Apr 12, 2007
  2. jcsd
  3. Apr 12, 2007 #2

    robphy

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    It seems that you have three unknown [rectangular] components, two at A and one at E.

    For the structure as a whole, did you write down Newton's laws (for statics) [tex]\vec F_{net}=\vec 0 [/tex] and [tex]\vec \tau_{net}=\vec 0 [/tex], which yields three scalar equations [for this planar problem].. and hence three linear equations in three unknowns? By choosing to evaluate moments about A, you can simplify your system.
     
  4. Apr 12, 2007 #3
    Right that is what I assumed! However, I'm kind of working backwards throught this text. So I'm not finding the correct moment equations.
     
  5. Apr 12, 2007 #4

    robphy

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    What are your explicit equations? (in terms of P1, P2, a, e)
     
  6. Apr 12, 2007 #5
    At pin A we have [tex] A_x and A_y[/tex] at the rocker E we have [tex] E_y[/tex].

    So shouldn't the moments be:

    [tex] M_A = 20kn-1.5A_y[/tex]

    I'm confused now! I know this is so easy when i finally see it
     
  7. Apr 12, 2007 #6

    robphy

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    Shouldn't it be "sum of the moments about A"
    [tex] M_A= (-1)(a)P_1+(-1)(3a)P_2+(1)(4a)E_y[/tex] ?
     
  8. Apr 12, 2007 #7
    Yes that is correct. I see now my mistake(s)
     
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