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Conservation and angular velocity

  1. Oct 30, 2011 #1
    1. The problem statement, all variables and given/known data
    I need help with this question: http://img804.imageshack.us/img804/2278/unledsbg.jpg [Broken]

    For a, I got omega = 18.63 rad/s by using methods of conservation of energy. Can someone tell me if I did this right? If not, please help me out! To be honest, I thought I had to use conservation of momentum for this since it involves a collision, but its equations dont involve angular velocity.


    2. Relevant equations

    Conservation of energy/momentum

    3. The attempt at a solution
    a) omega = 18.63 rad/sec
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Oct 30, 2011 #2

    Doc Al

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    Staff: Mentor

    Energy is not conserved. But angular momentum is.
     
  4. Oct 30, 2011 #3
    So does that mean I find v by means of conservation of momentum, and then use omega = v / r to find the answer? The reason I'm confused is because at the note at the bottom of the question, it says treat the door as a rod rotating about its end, which is a hint to use Inertia = (1/3)ML^2. Conservation of energy, not momentum, has inertia in its equation.
     
  5. Oct 30, 2011 #4

    Doc Al

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    Staff: Mentor

    Conservation of angular momentum will involve the moment of inertia.
     
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