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Homework Help: Tension in 2 cables

  1. Aug 31, 2010 #1
    1. The problem statement, all variables and given/known data
    A crane is used to lift a concrete pipe weighing 5kN into place.


    2. Relevant equations


    3. The attempt at a solution
    The picture is in my book, but i am certain my problem is in my algebra(i have the layout correct)

    T_ac*cos(20)=T_ab*sin(3.58) X direction
    5+T_ac*sin(20)=T_ab*cos(3.58) Y direction

    I am for some reason drawing a blank when it comes to how i can work this out, i tried solving for T_ac in equation 1 then plugging that into equation 2 but then i am running into an algebraic nightmare. One other problem aswell(its part of the question)

    I am given a triangle where Hypotenuse=4m and opposite=.25m, so using A^2+b^2=c^2 i got 3.99 for b. Then i used theta=arccos(adjacent/hypotenuse)=4.05, but for theta=arcsin(opposite/hypotenuse)=3.58. What am i doing wrong?
     
  2. jcsd
  3. Sep 1, 2010 #2

    rock.freak667

    User Avatar
    Homework Helper

    Since you didn't post a picture of the FBD, I will have to assume it is how I am expecting it to look.

    The equation for the x-direction should be

    Taccos(20)=Tabcos(3.58)

    and for y-direction

    5=Tacsin(20)+Tabcos(3.58)

    in which you'd just solve simultaneously.
     
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