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Ruler torque question

  1. Mar 31, 2008 #1
    1. The problem statement, all variables and given/known data
    A 30 cm ruler has a mass of 5g. Mark the pivot point and calculate the torque for the following situation:

    Ruler extends 10cm out from desk


    2. Relevant equations
    T= r x F

    F= |F|sinΘ

    F= m Fg

    3. The attempt at a solution

    F= mFg
    = (0.005kg) (9.8 m/s^2)
    =0.049 N

    T= r x F
    =|r||F|sinΘ
    =(0.10m)(0.049N) sin 90 degrees
    =0.00049 Nm

    The only thing Im not sure on is that only a third of the ruler is hanging off the desk so I am not sure if I have divide the mass.
     
  2. jcsd
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