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Homework Help: Angular momentum help

  1. Jun 16, 2009 #1
    A turntable has mass 4.96 kg and a radius of 0.092 m and is spinning with a frequency of 0.53 rev/s. What is the angular momentum??

    As simple as this problem seems, I just cannot seem to get the correct answer...here is what i have so far:

    I (for a disc) = (1/2)(mr^2)
    L = I(omega)
    I also know that angular momentum = frequency x I

    0.53rev/s(.5 x 4.96kg x 0.092^2) = 0.011 (kgm^2)/s
    However the correct answer is 0.0699....what am i doing wrong???
  2. jcsd
  3. Jun 16, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    L = Iω, where ω is in radians/sec.

    Convert to proper units.
  4. Jun 16, 2009 #3


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    Homework Helper

    The frequency is in revolutions per second; you need to convert it into radians per second. The conversion factor is [itex]2\pi\ \text{radians} = 1\ \text{revolution}[/itex].
  5. Jun 16, 2009 #4
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