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Homework Help: Find the tension forces

  1. Jan 27, 2010 #1
    A tank hanging off a hook, what are the tension forces?

    1. The problem statement, all variables and given/known data
    Determine the forces in cables AB, AC and AD needed to lift the tractor which has a mass of 8Mg.

    2. Relevant equations

    3. The attempt at a solution
    I found the unit vectors of the three rope forces using the ropes' position vectors.

    B = [-0.5241i -0.3276j -0.7861k]
    C = [-0.5241i 0.3276j -0.7861k]
    D = [0.31623i 0j -0.9487k]

    So F_B = -9.8bB, F_C = -9.8cC and F_D = -9.8dD where b, c, d = magnitudes of the forces

    Then I set up a system of equations to find b, c and d. I found:
    b = c = -1.691Mg
    d = -5.6218Mg

    |F_b| = |F_c| = 9.8*1.691E6 = 1.66E7 N
    |F_d| = 9.8*5.6218E6 = 5.51E7 N

    But I checked and they aren't the right answers. What did I do wrong?
    Last edited: Jan 28, 2010
  2. jcsd
  3. Jan 28, 2010 #2
    Can noone help? :(
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