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Rotating half cylinder energy and power calculation

  1. Dec 16, 2011 #1
    Hi folks,

    I'm an ocean engineer who's getting old and slow. If I have a half-cylinder mass on a shaft where I'd like to be able to quantify energy (which I think I have right) and then have some way of relating that to potential power output.

    What I have so far:
    m=18.6 kg
    Mass moment of inertia (I) = 0.5mr^2
    Rotational KE (Er) = 0.5Iw^2
    w=60rpm=0.159 rad/s

    I calculate the Er as 0.00747J

    Does this jive? Is there any meaningful way of relating that to power? I do not have a load value (yet), so am just trying to understand what this might be in terms of power if I use some conversion efficiency (thinking alternator load). I am assuming the same motive force that accelerated it to 60 rpm is constant (in some sort of resonance). If I have my calcs/assumptions wrong so far, please correct.
  2. jcsd
  3. Dec 17, 2011 #2


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    Welcome to Physics Forums.

    You're general approach is correct. However, 60 rpm is actual 2*pi rad/s. I get 0.90 J for the energy. (I=0.046 kg-m2)
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