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Rotational motion

  1. Dec 15, 2015 #1
    1. The problem statement, all variables and given/known data
    A 1.5 hp motor drives a machine disk having a mass of 4.5 kg and a diameter of .4 m from rest to a speed of 750 rpm. How long does it take to reach the operating speed?

    2. Relevant equations
    angular momentum
    torque
    3. The attempt at a solution
    I'm not really sure where to start with this problem. I don't know how to find time without distance or acceleration. I tried solving for acceleration but I'm not sure how horsepower relates to torque.
     
  2. jcsd
  3. Dec 15, 2015 #2

    haruspex

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    How much energy will the disk have at operating speed?
     
  4. Dec 15, 2015 #3
    How would I use that to find time?
     
  5. Dec 15, 2015 #4

    haruspex

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    What is the relationship between power, energy and time?
     
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