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Homework Help: Rotationlal dynamics quest

  1. Apr 27, 2008 #1
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    While i have done the work and believe i have followed the equations, I'm not confident of my answer as I dont understandt the relationship between the units im using. While Im pretty sure KE shoudl be in joules. I am guessing in the end.

    the question:
    Calculate the kinetic energy of a 1.00kg bicycle wheel with a diameter of 72.0cm when it is spinning about its axle at 180rpm. Assume that all the mass of the wheel is concentrated at its perimeter.

    my answer:
    KE=.5*I*om^2
    I=m*r^2 1.00kg*(.360m)^2 = .130kg*m^2
    omega = 180rev/m*6.28rads/60sec=18.84rad/s
    .5*.130kg*m^2*18.84rads/s=1.22J

    thanks
     
  2. jcsd
  3. Apr 27, 2008 #2

    Kurdt

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    You forgot to square the angular velocity. The units are fine.
     
  4. Apr 27, 2008 #3
    thanks!
    much appreciated
     
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