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Homework Help: Pendulum clock when taken to moon

  1. Dec 25, 2012 #1


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    1. The problem statement, all variables and given/known data
    A pendulum clock that keeps correct time on the earth is taken to the moon. It will run

    a) at correct rate
    b)6 times faster
    c)√6 times faster
    d)√6 times slower

    2. Relevant equations

    3. The attempt at a solution
    [itex]T_{earth} = 2\pi \sqrt{\dfrac{L}{g}} \\
    T_{moon} = 2\pi \sqrt{\dfrac{L}{g/6}} [/itex]

    Dividing i) by ii)

    [itex]\dfrac{T_{earth}}{T_{moon}} = \frac{1}{√6} \\
    T_{moon} = √6T_{earth} [/itex]

    This implies option c) is correct but my book says it is option d).
  2. jcsd
  3. Dec 25, 2012 #2


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    The period is longer so the frequency must be...
  4. Dec 25, 2012 #3
    Use concept ,

    T [itex]\alpha[/itex] 1/√g

    As √g reduces by √6 on moon , this implies time period on moon will be √6 times that of earth , as you got. You interpreted your answer wrongly. If the time period increases , pendulum will oscillate slower or faster for a given displacement of the bob ?
  5. Dec 25, 2012 #4


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    Thanks for pointing out my mistake
  6. Dec 25, 2012 #5


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    Forget the math for a minute and just think about it logically. Would you really expect a pendulum clock when moved to lower gravity to have the pendulum swing FASTER? Really ?
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