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Angular Momentum of a Tire (Help)

  1. Mar 12, 2009 #1
    Problem:
    A boy rolls a tire along a straight level street. The tire has mass 8.0 kg, radius 0.34 m and moment of inertia about its central axis of symmetry of 0.83 kg·m2. The boy pushes the tire forward away from him at a speed of 2.1 m/s and sees that the tire leans 10° to the right

    Compare the change in angular momentum caused by this torque in 0.20 s to the original magnitude of angular momentum.
    (change in momentum / original magnitude of angular momentum)

    Relevant formulas:
    L = Iw
    v = Rw
    L = rpsin(theta)

    Attempted Solution:
    w = 2.1m/s / .34 m = 6.176
    L = Iw = (.83)(6.176) = 5.126

    r = .2*2.1 = .42m
    p = (8kg)(2.1)= 16.8
    .42*16.8*sin(10) = 1.225

    1.225/5.126 = .239

    I was wondering if you could tell me what I'm doing wrong and walk me through the right process.

    Thanks
     
  2. jcsd
  3. Mar 12, 2009 #2

    berkeman

    User Avatar

    Staff: Mentor

    Moved to Homework Help forums.

    Woof. Not a simple problem. But this makes it overly hard/obscure:

    "Compare the change in angular momentum caused by this torque in 0.20 s to the original magnitude of angular momentum."

    The units of torque are not seconds...
     
    Last edited: Mar 12, 2009
  4. Mar 12, 2009 #3

    berkeman

    User Avatar

    Staff: Mentor

    Welcome to the PF, BTW!
     
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