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Pendulum bulb expriment

  1. Oct 23, 2012 #1
    1. The problem statement, all variables and given/known data
    There was this question involving a pendulum expriment:

    the five values of the square of the period (T^2) was plotted against the 5 values of the distance y in centimetre from the floor to the centre of the bob.

    I was then asked to determine the intercept on the vertical axis and slope of the graph as well; I have determined the intercept and slope of the graph.

    I was then asked to use the value of the intercept to determine the height H of the point of attachment of the pendulum to the floor. How do I go about that?


    2. Relevant equations



    3. The attempt at a solution
    I have gotten the intercept and the slope of the graph as well.
     
  2. jcsd
  3. Oct 23, 2012 #2
    You say that you know the distance from the floor Y and that you know the intercept (length of the rope)? Shouldn't the height of the point of attachment be H=y+L?
     
  4. Oct 24, 2012 #3
    Please what do you mean by 'L'?
     
  5. Oct 24, 2012 #4
    L - the length of the rope.
     
  6. Oct 27, 2012 #5
    I think I got the gist now:

    H = l+y
    ->
    l = H-y
    the value of the intercept that I got from the actual graph that I plotted is 4.55 (sec)2

    the period of oscillation of a simple pendulum is given as
    T = 2(pi)/w
    = 2(pi)(l/g)1/2

    since the intercept is at T2

    squaring both sides

    T2
    =
    (2(pi)(l/g)1/2)2

    we have
    (91/20)2
    =
    4(pi)2(l/g)
    =
    4(pi)2(H-y/g)

    assuming the acceleration due to gravity g is 10m/s and that the value of pi = 22/7

    (91/20)2
    =
    4(22/7)2(H-y/10)
    what do I subtitute in now as the value of the y?
     
    Last edited: Oct 27, 2012
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