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Homework Help: Strength Of Materials HW HELP

  1. Apr 26, 2012 #1
    1. The problem statement, all variables and given/known data
    I am having trouble with question 1 on the attachment posted. I understand that i need to get the area of the 2 bars. I am just not sure what to do with the forces. ALso i know the picture may be dark. P2 starts at point B and is pulling to the right and P3 starts at point C and is pulling to the left.

    2. Relevant equations
    I believe i use the equation A=∏d(^2)/4 to find the area but i am lost from there

    3. The attempt at a solution
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Apr 26, 2012 #2


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    Gold Member

    Looks like this is a test question. Perhaps you should do this on your own?
  4. Apr 26, 2012 #3
    Its Review for our final. Its an old test The question comes right out of our text book.
  5. Apr 26, 2012 #4
    after doing some research online i think i may be on the right track. The question is attchment #1 and my solution is attachment #2 .Please advise if i am doing this correctly. Thank you in advance

    Attached Files:

  6. Apr 26, 2012 #5
    I took that class last semester and you calcuations look correct to me, but then again i didnt ACE that class by any means
  7. Apr 28, 2012 #6
    3 things. Why do you use pi on what the question says is a square section?
    Your units of stress are not what an engineer would use. Have you drawn a normal force diagram, that is, a graph showing variation of axial load from one end to the other and checked it. If you had, and included the reaction I think you wouldn't have made the mistake you have for the force in AC.
  8. Apr 30, 2012 #7
    wow. I misread the question. I still believe i need to use the equation θ= P/A
    but now im not sure how to get the area of a square bar A= bh when only one dimension is given? I no whave no idea what my next step is. We have not covered normal force diagrams
  9. May 2, 2012 #8
    "im not sure how to get the area of a square bar A= bh when only one dimension is given?"
    What do you understand is the difference is between a rectangular section bar and a square section bar? Do you have a working definition of the axial force at a section?
    I have told you what a normal force diagram is. Can you sketch that by calculating the axial force at every section of the bar?
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