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What is the difference among moment, torque and couple?

  1. Oct 18, 2012 #1
    What is the difference among moment, torque and couple?

    Moment = Fd
    Torque = Fd
    Couple mean two forces have same magnitude but opposite direction.

    What is the relationship among them?
  2. jcsd
  3. Oct 18, 2012 #2

    Philip Wood

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    Gold Member

    Moment and torque mean exactly the same. You must always specify the point about which you are finding the moment (or torque) of a force. A given force will have different moments (or torques) depending on your choice of point.

    A couple is a pair of equal and opposite forces not acting in the same straight line. What's special about a couple is that the total torque of such forces is the same about whichever point we choose. It is given by
    [tex]G=Fd_{perp}[/tex] in which [itex]d_{perp}[/itex] is the perpendicular separation of the lines of action of the two forces. This is easy to show.
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