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Homework Help: Angular Momentum of a clock

  1. Nov 9, 2007 #1
    [SOLVED] Angular Momentum

    1. The problem statement, all variables and given/known data

    Find the magnitude of the angular momentum of the second hand on a clock about an axis through the center of the clock face. The clock hand has a length of 15.0cm and a mass of 6.00g. Take the second hand to be a slender rod rotating with constant angular velocity about one end.

    3. The attempt at a solution

    Clock hand: 15.0 cm --> .15m
    Mass: 6.00 g --> .006kg


    To get omega:
    The second hand does one revolution in 60seconds.

    so 1/60 = .01667 rev/s --> .10472 rad/s

    To get I:

    I = 1/3 ML^2

    I = (.006)(.15)^2 = .000135

    Now that we got I and omega,

    L = (.000135)(.10472)
    L = .0000141372

    I would have thought that this procedure would have been right, but I got it incorrect.

    Final Answer: L= _________ kg m^2/s

    Please and thank you. :smile:
  2. jcsd
  3. Nov 9, 2007 #2

    Doc Al

    User Avatar

    Staff: Mentor

    You forgot to multiply by 1/3.
  4. Nov 9, 2007 #3
    you have good eye. Thank you for your help. :)
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