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Homework Help: Force Problem and steel beam

  1. Feb 20, 2010 #1
    1. The problem statement, all variables and given/known data

    A 1000 kg steel beam is supported by two ropes. What is the tension in each?

    jl18p5.png


    2. Relevant equations

    F = ma = mg

    3. The attempt at a solution

    I labeled the left tension as [tex]T_{1}[/tex] and the right tension as [tex]T_{2}[/tex].

    [tex]\sum{F_{y}} = T_{1,y} + T_{2,y} -mg = 0[/tex]

    [tex]T_{1,y} = T_{1} cos(20^{o})[/tex]

    [tex]T_{2,y} = T_{2} cos(30^{o})[/tex]

    [tex]T_{1,y} = T_{2,y}[/tex]​

    [tex]\sum{F_{y}} = T_{2,y} + T_{2,y} -mg = 0[/tex]

    [tex]\sum{F_{y}} = 2T_{2,y} -mg = 0[/tex]

    [tex]2T_{2,y} = mg[/tex]

    [tex]2T_{2,y} = (1000kg)(9.8 m/s^2)[/tex]

    [tex]2T_{2,y} = 9800 N[/tex]

    [tex]T_{2,y} = 4900 N[/tex]

    [tex]T_{2} cos(30^{o}) = 4900 N[/tex]

    [tex]T_{2} = 5658 N[/tex]

    For [tex]T_{1}[/tex], I get [tex]5214 N[/tex].

    That answer is wrong. The answer should be [tex]6397 N[/tex] and [tex]4376 N[/tex].
     
  2. jcsd
  3. Feb 20, 2010 #2

    tiny-tim

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    Hi Cursed! :smile:
    Why?? :redface:

    And what about the x-components? :confused:
     
  4. Feb 20, 2010 #3
    Yeah. I figured that's probably where I went wrong.

    I don't know how else to relate the two tensions. :S
     
  5. Feb 20, 2010 #4

    tiny-tim

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    Hint: use the x-components!
     
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