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Homework Help: Rotational Inertia of a door

  1. Nov 13, 2005 #1

    Nm

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    A rotating door is made from four rectangular glass panes, as shown in the drawing. The mass of each pane is 76 kg. A person pushes on the outer edge of one pane with a force of F = 55 N that is directed perpendicular to the pane.
    09_34.gif
    a.) Find the rotational inertia of the door.
    b.) Find the magnitude of the door's angular acceleration.
    c.) Find the time it would take to rotate the door a half-circle (assuming it started from rest.)
    I have tried calculating the torque for the pane to be (1.2m)(55N) = 66 Nm. I think the rotational inertia should be I = 1/3ML^2 multiplied by 4 for each pane since it is spinning away from the center of mass (edge). Can someone tell me if this is correct? I don't know how to continue this problem...Thanks.
     

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  3. Nov 13, 2005 #2

    Nm

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    I figured out the solutions so never mind.
     
  4. Nov 14, 2005 #3


    I thought torque was rotational inertia multiplied by acceleration(in radians). You found your torque by multiplying the distance by the force? Can you exlplain your steps bcz I have a test on Friday on Rotation, and this could be very useful
     
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