Bifilar pendulum experiment

[houlahound]

Bifilar pendulum, data matches the theory real neat. Do have a question, I would expect the period to match the period of a torsional pendulum for the limit when the support strings are the same point ie zero separation.

I can't get the bifilar equation to reduce to the torsion equation for said limit. Any clues?

 

[lightgrav]

if the 2 pendulum strings are attached at the same point, it has become a simple ball-on-string pendulum.
(the bifilar's ball motion is the same as for a single string, if the string is shorter.)
A torsional pendulum's Restoring Force is caused by a thick support's rotational elasticity, rather than gravity.

 

[houlahound]

Not aware of the ball on string problem, google gave ambiguous results. Do you have link?