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Homework Help: Angular Speed

  1. Nov 6, 2008 #1
    1. The problem statement, all variables and given/known data
    A playground merry-go round of Radius R=2.00m has a moment of
    inertia I = 250 kg.m^2 and is rotating at 10.0 rev/min about a frictionless
    vertical axle. Facing the axle a 25.0kg child hops onto the merry go round
    and manages to sit down on the edge. What is the new angular speed of
    the merry go round?

    2. Relevant equations
    I = 250 kg.m^2
    10.0 rev/min
    25.0kg child
    radius = 2.00m

    I=r^2m
    L = r x p
    L = Iw

    3. The attempt at a solution

    I = r^2m
    m = I/r^2
    m = 250kg.m^2/(2.00m)^2 = 62.5kg

    I added the 62.5kg + 25.0kg = 87.5kg

    I = r^2m
    = (2.00m)^2(87.5kg) = 350kg.m^2

    I don't know what to do with this from here.
    Thanks for any help,
    Kevin
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 6, 2008 #2

    rock.freak667

    User Avatar
    Homework Helper

    Use the conservation of angular momentum
     
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