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Homework Help: About Torque a Equation

  1. Jan 20, 2010 #1
    A simple pendulum consists of a 3.0kg point mass hanging at the end of a 2.0m long light string that is connected to a pivot point.
    A. Calculate the magnitude of the torque (due to the force of gravity) around this pivot point when the string makes a 5.0 degree angle with the vertical.
    B. Repeat this calculation for an angle of 15.0 degrees.




    I do know that the torque equation is torque=forcexlever arm. Also that sinO is included. Also that the units for torque are NxM. I'm having some trouble figuring this out. Please help me. :)
     
  2. jcsd
  3. Jan 20, 2010 #2

    tiny-tim

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    Hi Kiko:)! :smile:

    (have a theta: θ :wink:)

    No, you don't use both lever arm and sinθ, you use one or the other.

    Either use force x (perpendicular) distance from pivot to line of force (= lever arm),

    or use force x distance from pivot to point of force x sinθ. :wink:

    (oh, and the unit is m, not M)
     
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