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-   -   Statics (Engineering) Tension and Reaction (https://www.askmehelpdesk.com/showthread.php?t=184642)

  • Feb 16, 2008, 10:01 AM
    jmrne961
    Statics (Engineering) Tension and Reaction
    A load of lumber weighing W=25kN is being raised as shown: http://i29.tinypic.com/2564idt.jpg by a mobile crane. Knowing that the tension is 25 kN in all portions of cable AEF and that the weight of boom ABC is 3 kN, determine:
    a. the tension in rod CD
    b. the reaction at pin B

    answers: part a: tension in CD=81.1kN part b: 134.1kN up.

    I don't understand this problem much, but here's my attempt to solve it. I've spent about 3 hours looking at it trying to figure out ways to do it...
    Sum of Forces in x-direction= 0. at Pin B, there is no force in the x-direction
    Sum of forces in y-direction=0.
    therefore, -W-3-25-(CD)=0, but that's not right.
    Sum of moments at any point (lets say B)=0.
    Therefore, 25(2.6)+.6(3)+.4(25)+.7(CD)=0 and so CD=109.7, which is also incorrect.

    Can someone PLEASE help? Thanks.
  • Nov 5, 2010, 08:59 PM
    Tunguoge
    Part A
    the summation Mb=0
    (25kN*2.6) + (3kN*0.6) - (25kN*0.4)- Tcd*(0.7) = 0
    0.7Tcd= 56.8kN
    Tcd = 81.1kN

    Part B

    for Summation F= 0
    SumFx=0
    Bx=0
    SumFy=0
    By= 25kN+3kN+25kN+81.1kN=134.1 kN up

    hope that help

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