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Homework Help: Angular speed question please help right away!

  1. Dec 14, 2004 #1
    angular speed question!! please help right away!

    a pencil, 15.7 cm long, is released from a vertical position with the eraser end resting on a table. The eraser does not slip. Treat the pencil like a uniform rod. what is the angular speed of the pencil just before it hits the table?

    i know i have to use conservation of energy, but im not sure where center of mass fits in.. please help

    the answer choices are:
    a. 11.2 rad/s
    b. 7.23 rad/s
    c. 24.5 rad/s
    d. 16.8 rad/s

    any help or guidance would be much appreciated..thank u!
  2. jcsd
  3. Dec 14, 2004 #2

    Doc Al

    User Avatar

    Staff: Mentor

    In figuring the change of PE of the pencil, use the change in height of the center of mass. The PE gets converted to rotational KE.
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