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Engineering Statics Question

  1. Sep 17, 2012 #1
    1. The problem statement, all variables and given/known data

    http://imgur.com/a/FyekZ
    I took the liberty of uploading everything. The first picture is the question, while the other two is my attempt at answering it in two parts. What I do not understand is what I did wrong or where I went wrong.
    I also would like to know why, unlike many other questions from the text, this question does not specify in which direction the resultant force is directed. Is the question wrong, or am I supposed to go about this in a different manner?

    EDIT: If you cannot see the full image, please click the gear icon (top right of each image - gear appears when you have the mouse over the image) and select view full resolution.

    2. Relevant equations

    See above.

    3. The attempt at a solution

    Please see above.
     
  2. jcsd
  3. Sep 18, 2012 #2

    CWatters

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    Deleted.
     
    Last edited: Sep 18, 2012
  4. Sep 18, 2012 #3

    CWatters

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    Ok so there appears to be too many unknowns unless you assume the resulting force is to be in the "u" direction.
     
  5. Sep 18, 2012 #4

    CWatters

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    I think you may have made an error in the calc for Fry. Did you forgot to divide by Sin(28)?
     
  6. Sep 18, 2012 #5

    CWatters

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    Actually it looks like you can calculate the angle of the resultant. Call that β then..

    In x..

    FR*Cos(β) = F1*Cos(θ) - F2*3/5 + F3*Cos(45)
    so
    F1*Cos(θ) = FR*Cos(β) + F2*3/5 - F3*Cos(45) ............(1)

    In y..

    FR*Sin(β) = F1*Sin(θ) + F2*4/5 - F3*Sin(45)
    so
    F1*Sin(θ) = FR*Sin(β) - F2*4/5 + F3*Sin(45)................(2)


    Knowns F2, F3, FR, θ
    Unknowns F1 and β

    We have two equations and two unknowns.
     
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