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Homework Help: Rotational Dynamics and torque, easy problem

  1. Apr 2, 2004 #1
    I really have no idea how to go about doing this one.... Any help is well appreciated! Thanks!!!

    What is the angular acceleration of the rectangle in (attachment) if a torque of 13 Nm is applied about (a) the x axis (b) the y axis and (c) the z axis (through origin and perpendicular to the page).

    I assumed I would use t=Ia where I would simply be m*r^2. But that gives me the wrong answer.

    The answers are (a)2.4 (b)5.1 (c)3.0 if that helps.
  2. jcsd
  3. Apr 2, 2004 #2


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    This question is a bit obnoxious because it's unclear whether the object is forced to rotate on the axes you meantion.

    Regardless, can you calculate the moment of inertia of the object about the x,y, and z axes of the object?
  4. Apr 2, 2004 #3
    I assumed the axes rotated with the system (around the center of the rectangle). But then I guess the radius would be the same and the angular acceleration would just be equal and opposite for (a) and (b) (clockwise and counterclockwise rotation). And all I really know about calculating moment of inertia is plugging whats given (or found) in a problem into a given set of I's provided in class. Your right this is kind of an iffy system....Sorry. But thanks anyways!
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