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Homework Help: Tough systems of equations

  1. Feb 13, 2010 #1
    1. The problem statement, all variables and given/known data

    I've got this physics problem where I'm working to find the magnitudes of two force components.

    2. Relevant equations

    F1sin45 + F2cos30 = 500 lbf

    F1sin45 - F2sin30 = 0

    3. The attempt at a solution

    I've tried so many times by substituting F1 and F2 into both equations but I just can't seem to solve for them. Can someone guide me on how to solve this particular problem step by step because I have to solve a bunch of these.
  2. jcsd
  3. Feb 14, 2010 #2


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    Gold Member

    Can you show us exactly what you are doing to solve the system?

    What you could do is re-arrange the second equation to get F1 in terms of F2 and then substitute it into the first equation.
  4. Feb 14, 2010 #3


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    Homework Helper

    Both equations 1 and 2 contain F1sin45, you can just subtract equations 1 and 2, and get F2, remember sin30°=1/2 and co30°=√3/2
  5. Feb 14, 2010 #4
    You can add, divide, subtract equations when dealing with systems.
  6. Feb 14, 2010 #5
    Ok I did what you said, but I end up with this:

    F2(√3/2) + F2(1/2) = 500

    How do I get F2 alone now?
  7. Feb 14, 2010 #6
    (root 3 +1)F_2/2=500
    1000/(root 3+1)=f_2
  8. Feb 14, 2010 #7
    I got 577.35 for F2. Is that right?
  9. Feb 14, 2010 #8
    no. its [tex]\frac{1000}{\sqrt{3}+1}[/tex]
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