1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook