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Homework Help: Moment of Inertia of a uniform rectangular coil

  1. Mar 29, 2010 #1
    1. The problem statement, all variables and given/known data

    A uniform rectangular coil of total mass 270 g and dimensions 1m x 5m is oriented perpendicular to a uniform 4.00-T magnetic field (the figure ). A current of 2.90 A is suddenly started in the coil.

    2. Relevant equations

    angular acceleration = torgue / moment of inertia

    3. The attempt at a solution

    Here is the image...

    It rotates around axis 2


    I can't figure out how to find the moment of inertia of this shape. I know the basic formula, of moment of inertia and how you find it, but can't figure out how to tell how the mass is distributed. I'm pretty sure the parts of the rectangle that are parallel to the axis of rotation can be excluded, because they will cancel each other out, but the bars on the side are confusing me.

    Any help is greatly appreciated.
  2. jcsd
  3. Mar 29, 2010 #2


    User Avatar
    Homework Helper

    I am assuming axis 2 is the horizontal axis.

    So just use the formula for the moment of inertia about the x-axis for a rectangular lamina.

    Also, it is uniform, the mass acts at the geometric center of the rectangle.
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