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!

Find tension and Direction

  1. Mar 7, 2010 #1
    During a storm, a tree limb breaks off and comes to rest across a barbed wire fence at a point that is not in the middle between two fence posts. The limb exerts a downward force of 164 N on the wire. The left section of the wire makes an angle of 12° relative to the horizontal and sustains a tension of 447 N. Find the magnitude and direction of the tension that the right section of the wire sustains.
    I got the tension in the rope which is 440N, I am having trouble finding the Direction.

    ° (counterclockwise from x-axis) ?

    I tried 1/cos of 164/440...its wrong

  2. jcsd
  3. Mar 7, 2010 #2


    User Avatar
    Homework Helper

    how did you get 440 N?
    you _should_ keep vertical Forces and horizontal Forces separate .
  4. Mar 7, 2010 #3
    i will look thru my notes and see how i came to it.
  5. Mar 7, 2010 #4
    this is how i got the 440N: we break the tensions into x- & y- components

    So x- direction....-447N*cos(12) + T2*cos(θ2) = 0...So T2*cos(θ2) = 437.2 [eqn 1]
    and in the y- direction 447*sin(12) + T2*sin(θ2) - 146 = 0..
    so T2*sin(θ2) = 146 - 447*sin(12) = 53.1 [eqn 2]

    Now divide eqn 2 by eqn 1 giving sin(θ2)/cos(θ2) = 53.1/437.1

    or tan(θ2) = 0.1214....so θ2 = arctan(0.1214) = 6.92o

    Now plug back into eqn 1 to get T2...T2 = 437.1/cos(6.92) = 440N
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook