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Homework Help: Torque on a rigid body

  1. Dec 9, 2007 #1
    1. The problem statement, all variables and given/known data
    prove that when the net force on a rigid body is zero, the torque about any line perpendicular to the plane of the forces is equal.

    2. Relevant equations

    3. The attempt at a solution
    it is known that angular velocity, and hence angular acceleration about any line is the same for a given rotating rigid body.
    implies, [tex]\alpha[/tex] is same about all lines.
    if we accept the above statement to be true, then I comes out to be equal about every axis, which is a contradiction.
  2. jcsd
  3. Dec 9, 2007 #2
    If it's perpendicular the the cross-product will just be tau = |r||F|
    Last edited: Dec 9, 2007
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