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Homework Help: Speed of Pivoting Rulers

  1. Dec 13, 2008 #1
    1. A .200 kg stick pivots about one end. The meter stick starts balanced above this pivot. What would be the speed of the center of mass of the meter stick at the bottom of the swing?

    2. Torque=force sin (theta)*radius

    3. The torque acting on the object is .981 N*m (9.81*.2*sin 90*.5) (sin 90 because it is 90 degrees above the horizontal axis.)
    But how do you get angular velocity from torque? I also know that torque=moment of intertia*angular acceleration. But how do you get angular velocity from this?
    Is this even a torque problem?
  2. jcsd
  3. Dec 14, 2008 #2


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    Welcome to Physics Forums,

    You can indeed solve this problem by considering the torques acting on the ruler. However, it may be somewhat simpler to consider conservation of energy.
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