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Homework Help: Angular momentum Question

  1. Jan 7, 2012 #1
    1. The problem statement, all variables and given/known data
    Harry Potter is sitting 2.0 meters from the center of a merry-go-round when Draco Malfoy casts a spell that glues
    Harry in place and then makes the merry-go-round start spinning on its axis. Harry has a mass of 50.0 kg and can
    withstand 5:0 g's of acceleration before passing out. What is the magnitude of Harry's angular momentum when
    he passes out?

    2. Relevant equations
    T=I alpha

    3. The attempt at a solution

    Assuming that the spell is a force then rF = I alpha. And using alpha = a/r, we using the max acceleration of 5g that
    5mgr = Ia/r
    However I'm not sure where to go from this, how do i get v? as time is unknwon
  2. jcsd
  3. Jan 7, 2012 #2
    Lets look at the second eqn you mentioned,
    you have m,r. what you need is v

    Now, what do you think the acceleration 5g is acting along (direction)?
  4. Jan 8, 2012 #3
    oh i see mv^2/r = ma a=5g :D
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