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Homework Help: Static equilibrium problem due tomorrow evening

  1. Nov 12, 2007 #1
    1. The problem statement, all variables and given/known data
    A 0.105 kg meter stick is supported at its
    40 cm mark by a string attached to the ceiling.
    A 0.665 kg object hangs vertically from the
    7.17 cm mark. A second mass is attached
    at another mark to keep it horizontal and in
    rotational and translational equilibrium.

    If the tension in the string attached to the
    ceiling is 21.2 N, find the value of the second
    mass. Answer in units of kg.

    2. Relevant equations
    The acceleration of gravity is 9.8 m/s2
    Sum of Forces= 0
    Sum of Torques =0

    3. The attempt at a solution

    Since the sum of the forces =0
    21.2N - 0.665kg*9.8m/s2 - x*9.8m/s2 = 0
    1.47786 kg

    I'm not sure why this isn't right or how to fix it
  2. jcsd
  3. Nov 12, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You left out the mass of the stick itself.
  4. Nov 12, 2007 #3
    Got it, thanks so much!!
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