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Inertia Question

  1. Apr 30, 2012 #1
    1. The problem statement, all variables and given/known data

    The full metal wheel of radius 30 cm, 300 kg of mass moment of inertia I = 1/2 (mr ^ 2) operating torque 50nm in time 1 min. Determine the angular acceleration, angular speed of wheel, revolutions per second, revolutions that the wheel makes to achieve this speed, kinetic energy.

    2. Relevant equations

    ω = 2∏/T, s=1/2(αt^2), Ek=(Iω^2)/2, I = 1/2 (mr ^ 2)

    3. The attempt at a solution

    First I can get ω, T=60sec, so ω=∏/30...

    So I can get all of this using those few formulas, but in the end I get kinetic energy in mJ??
     
  2. jcsd
  3. Apr 30, 2012 #2

    SammyS

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    Why not get kinetic energy in Joules ?
     
  4. Apr 30, 2012 #3
    I can get energy in Jules but then its very small number, but i dont get it why is a small number?
     
  5. Apr 30, 2012 #4

    gneill

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    The torque is acting for 1 minute; The given time of 1 minute is not the period of oscillation or rotation...
     
  6. Apr 30, 2012 #5
    Okay. I got it! Now its Ek=7,5kJ
     
  7. Apr 30, 2012 #6

    gneill

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    Perhaps you should elaborate on your calculations; To me, 7.5 kJ doesn't look right.
     
  8. Apr 30, 2012 #7
    M=F*r
    F=m*α
    α=ω/T
    Ek=(Iω^2)/2
     
  9. Apr 30, 2012 #8

    gneill

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    I see a collection of formulas, at least one of which is rather dubious, but no calculations. Can you show your numerical work and explain what the steps are that your taking?
     
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