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Pendulum test?

  1. Feb 2, 2013 #1
    morning ladies n gents

    just wondering has anyone studied this physics experiment before? I have to do it as part of my last year at uni as I didnt do physics at college ( chose mechanics much more interesting!)

    anyway its apparently been the same exam for the last 4/5 years but the lecturers give you no help in advance and just give you this equation:

    T = 2 * Pi * sqrt(l / g)

    T = period (in seconds)
    Pi = 3.14...
    sqrt = root of ...
    l = length of pendulum in m
    g = acceleration in m/s^2 (9.81)

    I am wondering if anyone has done this experiment but working out G rather than t? if so what would the formula be rearranged? I have found 2 through some googling :

    1. g = l/(t/tpi)^2
    2. g = 4pi^2L/T^2

    Sorry if this is in the wrong section please move if it is
     
  2. jcsd
  3. Feb 2, 2013 #2

    tiny-tim

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    good morning, donniemateno! :wink:
    square this equation, then re-arrange it …

    what do you get? :smile:
     
  4. Feb 2, 2013 #3
    Quote by donniemateno
    T = 2 * Pi * sqrt(l / g)
    square this equation, then re-arrange it …
    what do you get?

    g = sqrt (2*pi*l )/ T?
     
  5. Feb 2, 2013 #4

    tiny-tim

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    hi donniemateno! :smile:

    why aren't there more squares there? :confused:
     
  6. Feb 2, 2013 #5
    g = sqrt (2*pi*l )/ T^2

    I think

    Im really not very good at rearranging formulas

    I understand the concept of taking one from one side to the other through division but get lost when sqreroots are involved
     
  7. Feb 2, 2013 #6
    a square roots becomes a ^2 so does that mean:

    g =(2*pi*l)^2/ T^2
     
  8. Feb 2, 2013 #7

    tiny-tim

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    ok, then do it one step at a time :wink:

    first, square T = 2 *π* √(l / g) without any rearranging …

    what do you get? :smile:
     
  9. Feb 2, 2013 #8
    first, square T = 2 *π* √(l / g) without any rearranging

    I'm going to say

    T^2=2*pi*(l/g)?
     
  10. Feb 2, 2013 #9

    tiny-tim

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    T2 correct :smile:

    (l/g) correct :smile:
     
  11. Feb 2, 2013 #10
    is the next step to divide by 2 pi? if so would that be :

    T^2 / 2*pi = (l/g)?
     
  12. Feb 2, 2013 #11

    tiny-tim

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    whoa!!

    go back … your 2 *π was not correct …

    you needed to square it! :wink:
     
  13. Feb 2, 2013 #12
    would pi become 4 pi?
     
  14. Feb 2, 2013 #13

    tiny-tim

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    yup! :smile:

    T = 2 *π* √(l / g)

    becomes

    T2 = 4 *π2* (l / g) :wink:

    (you see how you have to square each term separately?)

    ok, now get g on the left and T2 on the right :smile:
     
  15. Feb 2, 2013 #14
    so next if i divide by g to get

    T2 / g = (4 *π2* (l / g)) / g

    then divide by t^2 to move it over giving me

    g = (4pi*l)/T^2
     
  16. Feb 2, 2013 #15

    tiny-tim

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    divide by g?? :confused:
     
  17. Feb 2, 2013 #16
    would it become

    t^2*g = 4pi^2*l

    then

    g = 4pi*l / T^2?
     
  18. Feb 2, 2013 #17

    tiny-tim

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    (you mean g = 4pi2*l / T2 :wink:)

    yes!! :smile:
     
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