sci.physics.research

On Sep 5, 8:02 am, Edward Ruden wrote:

> I've uploaded my old final report to
> /~rudenbiz2/physics/pubs/

Many thanks for posting your Cavendish lab paper. I have been looking
to find the equation of motion for the experiment for a while now.
Recently I came across this page

/tcs/weeklyIssues_2005/2005-07-01/feature1/

which has the same differential equation but I couldn't figure out the
solution. It was a nice surprise to find that you have the solution as
well.

I have many questions. But first I would like to find the solution
without the simplifying assumption that you make

x = theta d << a

and compare it with the solution you actually used in your experiment.
Do you know that solution?

How did you obtain w_0^2? In pendulum motion w^2 = K/I, I understand
that part. But I couldn't figure out the algebra for the second term
4GMmd^2/Ia^3.

I also tried to simplify the equation of motion by ignoring damping
due to air. I assumed that R=0 and that eliminated the exponential. I
also eliminated the phase angle phi and also substituted B and w_0^2
and w_0 to see the constant terms explicitly. Since it is difficult to
write those equations in the newsgroup I put them in my wiki.

/wiki/ ?title=Cavendish_experiment_%28equation_of_motion%29

As far as I understand, using this equation of motion we add a
constant factor to the trigonometric simple harmonic motion of the
pendulum. Did you notice in your measurements the effects of the force
in the pendulum motion? How did the the pendulum arm vary because of
the force term?

Thanks again, this was very helpful.