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Homework Help: Physic problem

  1. Dec 9, 2006 #1
    If a wheel is turning at 3.0 rads/s, the time it takes to complete one revolution is about:

    3.0 rads/s X 1 revolution/6.28 rads = .477 revolutions/s
    now do I just times by 60s to cancel the seconds out to get 1 revolution.


    The rotational speed of the minute hand of a watch is:

    w= anglular displacement/ time
    w=2pi radian in a circle/ 3600 seconds in one rotation --> pi/1800 rad/s
    is that right?
     
  2. jcsd
  3. Dec 9, 2006 #2

    marcusl

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    No, that would give the number of revolutions in 60 seconds. How do you think you can get an answer in seconds/revolution?

    How many seconds in a minute?
     
  4. Dec 9, 2006 #3
    For the first problem I just want the answer in seconds, not seconds/revolutions

    I put 3600 seconds because it is the amount of time for the minute hand to make one full revolution around the clock
     
  5. Dec 10, 2006 #4

    marcusl

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    Understood. If the wheel makes 0.477 revolutions in 1 second, then the time it takes to make 1 rev is 1/0.477 = 2.094 seconds. You need to take the inverse of the speed (that gives sec/rev) and multiply by the number of revolutions (in this case 1).
    Oops, that's my mistake! :blushing: Your answer is correct.
     
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