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  Computation of G from Cavendish experiment

  I used original data from the Cavendish experiment to compute the value of G. My computation yielded a value for G 2.67 times greater than the recommended value:

  G(Cavendish) = 1.78424*10^-7 cm^3 sec^-2 g^-1

  G(recommended) = 6.67428*10^-8 cm^3 sec^-2 g^-1

  I used the well-known method of equating the torque of torsion wire (k theta) and the torque of gravity (GMmL/s^2) and solving for G:

  G = k theta s^2 / MmL

  k = torsion constant = 724.68 g cm^2 sec^-2
  theta = excursion angle from mid-point = 0.0054788 radians
  s = distance between weights = 21.97 cm
  M = big weight = 158100 g
  m = small weight = 729.8 g
  L = gyration arm = 93.09 cm

  More information about the geometry of the experiment can be found here. I would be grateful for any corrections and comments. Thank you.

  Posted 26 Aug 07 in Cavendish Experiment

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  Moment of Inertia of the Cavendish pendulum

  Posted this to Physics Forum:

  Ok. Thanks. From hyperphysics I got 1/12 M L^2 and added it to the previous result:
  
  I = 2 m r^2 + 1/12 M L^2
  
  L = length of the rod
  r = half length of the rod
  
  So,
  
  Total moment of inertia for the Cavendish experiment = r^2 (2m + 1/3M) = 13,137,851.84 cm2 g
  
  m = weight of each ball = 729.8 g
  
  M = Rod weight = 155.5 + 11 + 2.9 = 169.40 g (including deal rod, silver supporting wire, vernier attached to the arm)
  
  L = Rod length = 73.3 inches = 186.18 cm
  
  r = Half rod length = 93.09 cm
  
  I also added another picture with a little more detail about the arm. (Figure 3 here.)
  
  Does this look good?
  
  Thanks again for your help.

  Posted 19 Aug 07 in Cavendish Experiment

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  Forces acting in Cavendish experiment

  In the Physics Forum Doc Al wrote that "there are two forces acting on the small masses: Torsion (kr) and gravity."

  Is this metaphorical type of speaking? How can the torsion of the wire can be said to act on the lead balls attached to the pendulum? I know that physicists use their own jargon. Maybe this is a statement that should not be taken literally?

  Posted 12 Aug 07 in Cavendish Experiment

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  Experiment IV - Chart showing extreme points of the arm

  Make that 210 years ago. He made the experiment on August 12, 1797.

  Posted 12 Aug 07 in Cavendish Experiment

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  Occult does not exist in nature

  Newtonian force is occult. There is no occult in nature. Therefore force does not exist in nature. Therefore, Cavendish did not observe the occult force. Do you agree?

  Cavendish scandal

  Posted 07 Aug 07 in Cavendish Experiment

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  Was Cavendish experiment a precise experiment?

  Not according to my definition of precise. Cavendish built his pendulum and placed it in a shed in his backyard. He then left it there for a year. During one year he made just 17 experiments. He calibrated the pendulum only once before he made his first measurement. During one year, the tension of the copper wire changed, the distances between weights changed. Cavendish ignored all these. What do you think. Are these signs of a precise experiment?

  Posted 05 Aug 07 in Cavendish Experiment

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  Did Cavendish measure the Newtonian force?

  This is great! I like tangler.

  I missed that lecture too. I studied the experiment on my own. It is really simple and fun. Cavendish suspended a wooden beam (2 meters long) by a  copper wire and hung lead weights of 2 inch diameter on each end. He then brought heavier weights near the pendulum and measured the oscillations of the pendulum arm. He then computed the mean density of the earth.

  My humble opinion is that Cavendish's pendulum never moved under the influence of the Newtonian force because Newton's force is occult and occult does not exist in nature. Professional physicists disagree with this. So I have been trying to find a good test to try when duplicating the experiment to verify if Cavendish did or did not measure the Newtonian force.

  Henry Cavendish at Wikipedia 

  Posted 03 Aug 07 in Cavendish Experiment