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Motion's frequency

  1. Sep 25, 2013 #1
    A electric model train travels at 31.7 cm/s around a circular track of radius 1.73 m.

    How many revolutions does it perform per second, i.e, what is the motion\'s frequency?
    ______ Rev / s

    Find the train\'s period of revolution.
    ______ s

    This is how I worked my problem out:
    v^2/r = rw^2
    .317^2/1.73 = 1.73w^2
    .317^2/1.73^2 = w^2
    w = 0.18323699421 radians per second.
    there are 2 pi radians, so it takes 2pi radians / .1832 radians/second = seconds

    34.2 seconds
    1.75 revolutions per second (60/34.2)

    I'm getting that the 1.75 is wrong and I don't know why or how. Help please
  2. jcsd
  3. Sep 25, 2013 #2


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    Science Advisor

    Is this homework ?
  4. Sep 25, 2013 #3
    Yes, it's online. That's why I don't know why this answer is wrong
  5. Sep 26, 2013 #4


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    You are making it far too difficult. Always go back to first principles.
    Work out the length of the track,
    you know how fast the train is travelling so,
    you can work out the time needed per revolution.
  6. Sep 26, 2013 #5


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    Staff: Mentor

    You calculated the revolutions per minute, not per second.
    If it takes 34.2 seconds for one revolution, you will certainly not have more than one revolution per second!
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