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Homework Help: Bar and weights

  1. Apr 11, 2009 #1
    A beam of mass mb = 10.0 kg, is suspended from the ceiling by a single rope. It has a mass of m2 = 40.0 kg attached at one end and an unknown mass m1 attached at the other. The beam has a length of L = 3 m, it is in static equilibrium, and it is horizontal, as shown in the figure above. The tension in the rope is T = 637 N.

    a) Determine the distance, x, from the left end of the beam to the point where the rope is attached. Note: take the torque about the left end of the beam.

    I know that M1 is 15 kg. I keep getting 4 m from the point of rotation but thats wrong. here is the help they told me, but i just dont think it makes sense at all:

    HELP: We know the sum of the torques will be zero. Since we are taking the torque about the left end of the beam, there are only three torques we will need to deal with.

    HELP: We can assume the beam is uniform in distribution of mass and therefore take the torque of the beam at the center, 1.5 meters. Remember that the torque is the force time the perpendicular distance, i.e. be careful with the distances you choose. The torque is zero about every point, and therefore you can take the torque about another point as a check.
  2. jcsd
  3. Apr 11, 2009 #2


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    It would be helpful if you showed your calculations. We have no way of knowing what you did otherwise.
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