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: Static equilibrium - quarry crane

  1. Mar 24, 2009 #1
    1. The problem statement, all variables and given/known data

    A quarry crane is used to lift massive rocks from a quarry pit. Consider the simplified model of such a crane shown in the figure. The ends of two poles are anchored to the ground at the same point (point O). From this point, one pole rises vertically and the second pole rises at an angle. The vertical pole has its free end connected to the ground via an unstretchable, massless rope labeled rope 1. A second rope, labeled rope 2, connects the free ends of the two poles. The angle between the tilted pole and rope 2 is θ. Both poles have length and can be considered massless for the purposes of this problem. Hanging from the end of the second pole, via rope 3, is a granite block of mass m.

    Throughout this problem use g for the magnitude of the acceleration due to gravity.

    Find T2, the tension in rope 2.

    2. Relevant equations

    At static equilibrium, sum of torque=0, sum of forces = 0.

    3. The attempt at a solution

    I think I need to use sum of torque (about point O??) but how? I don't understand the qns/ diagram..... Please help! Thanks:)

    Attached Files:

    • 12.jpg
      File size:
      12 KB
  2. jcsd
  3. Mar 24, 2009 #2


    User Avatar
    Homework Helper

  4. Mar 27, 2009 #3
    I tried to derive the answer from the hints given in that thread but I still got it wrong. :(

    There's also another part to the question:
    Find T1, the tension in rope 1.

    Please help!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook