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Find the acceleration due to gravity

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  1. Mar 23, 2016 #1
    1. The problem statement, all variables and given/known data
    A person shakes pendulum with length 3.6 meters. For 12 shakes he measured the time of 38 seconds. Find the acceleration due to gravity

    2. Relevant equations
    T=t/n
    T=2*pi*sqrt(l/g)

    3. The attempt at a solution
    T(period)=t/n=3.167
    T=2*pi*sqrt(l/g) l-length
    g=4*(pi)^2*l/T^2
    g=14.156
    The solution in my book is 9.4 m/s^2. Where is my error?
     
  2. jcsd
  3. Mar 23, 2016 #2

    gneill

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    Staff: Mentor

    Your solution method looks fine.

    Perhaps there's an error in the book (Sometimes they update problems with new editions but fail to update the answer key), or there's something about the definition of "shakes" that we're missing. Is the problem statement a translation?
     
  4. Mar 23, 2016 #3
    Yes
     
  5. Mar 23, 2016 #4

    gneill

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    What is the original language? Is there more information in the original problem statement that you haven't shown?
     
  6. Mar 23, 2016 #5
    I have given all the information. The correct answer is 9.4 m/S^2
     
  7. Mar 23, 2016 #6

    gneill

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    Your answer is correct (if you round to the correct number of significant figures). I don't agree with the book's answer.
     
  8. Mar 23, 2016 #7

    gneill

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    Was the pendulum a simple pendulum (mass bob on a string) or something else, like a solid rod?
     
  9. Mar 23, 2016 #8
  10. Mar 23, 2016 #9

    gneill

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  11. Mar 23, 2016 #10

    gneill, did you use paint to draw that picture or what program did you use, i really want to know . Sorry for saying something not related to OP
     
  12. Mar 23, 2016 #11

    gneill

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    The picture came from the OP's link. I just cut-and-pasted it to make it visible in-thread; off-site links have a tendency to disappear over time.

    I do make quite a few images for posting here though. I use an old version of Visio to make them.
     
  13. Mar 23, 2016 #12
    many thanks to you
     
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