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!

Please help! Statics

  1. Jul 5, 2009 #1
    1. The problem statement, all variables and given/known data
    A mass M=171 kg is suspended from the end of a uniform boom as shown. The boom (mass=83.0 kg, length=2.40 m) is at an angle θ=69.0 deg from the vertical, and is supported at its mid-point by a horizontal cable and by a pivot at its base. Calculate the tension in the horizontal cable.

    http://i32.photobucket.com/albums/d2/NikkiNik88/staticsboom.gif

    2. Relevant equations

    T=rsin(theta)

    3. The attempt at a solution

    Theta = 69 deg, alpha=21 deg

    mg(L/2)cos(theta) + Mg(L)cos(theta) + T(L/2)sin(alpha) = 0

    When I solved for T I got 4169.25N but that is incorrect please help
     
  2. jcsd
  3. Jul 5, 2009 #2

    ideasrule

    User Avatar
    Homework Helper

    Why are you using cosine for mg(L/2) and sine for the others, instead of the other way round? Think more carefully about which functions you should use.
     
  4. Jul 5, 2009 #3
    Would I be using sine for the masses because they are vertical and cosine for the tension because it's horizontal? If that's the case, is the rest of my work correct if I switch sine and cosine?
     
  5. Jul 5, 2009 #4

    ideasrule

    User Avatar
    Homework Helper

    Yes! So:

    mg(L/2)sin(theta) + Mg(L)sin(theta) + T(L/2)cos(theta) = 0

    The answer you get will be negative, but that's only because the tension acts to counteract the torque applied by gravity.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Please help! Statics
  1. STATICS please help (Replies: 5)

Loading...