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Homework Help: Angular Momentum: mud hitting door

  1. Nov 19, 2011 #1
    1. The problem statement, all variables and given/known data
    A solid wood door 1.00m wide and 2.00m high is hinged along one side and has a total mass of 42.0kg. Initially open and at rest, the door is struck at its center by a handful of sticky mud with mass 0.500kg, traveling perpendicular to the door at 14.0m/s just before impact.
    Find the angular speed of the door.

    2. Relevant equations


    3. The attempt at a solution



    I'm not sure how to calculate [itex]I_{door}[/itex], which gets me stuck here.
    I had read online that it is:


    Mud I know:


    Assuming I calculated the door correctly,




    But this is wrong, and I'm not sure where I messed up. Thanks in advance!
  2. jcsd
  3. Nov 19, 2011 #2
    I figured out the correct answer, but in order to get it, I needed to say that


    I don't understand why I should use 1 for the radius of the door, when the force was applied to the centre of the door.
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