Re: [Phys-l] "compound" pendulum

[Bernard Cleyet <bernardcleyet@redshift.com>]

Compound is the name horologists use, which is for them a pendulum of great interest.**   It is a idealized form of the physical pendulum whose equation of motion is solved in intro. texts and the period is found by horologists.

John Haine*** uses the torques/moments of inertia method (which you used, and, I presume, do all the intro texts) to find the equation of motion (small angle approx.) and from that the period.

The problem you have w/ the Newtonian method illustrates the advantage of the Euler-Lagrangian formulation, which I suspect one can use.  It  ignores forces, only involving the KE and U (potential energy) as a function of generalized coordinates.

** The method of realizing long periods in confined spaces.

*** Horological Science Newsletter 2008-3

bc

On 2010, Dec 03, , at 19:14, Stefan Jeglinski wrote:

> I doubt "compound" is the correct description - if it has a proper 
> name I'd like to know what it is.
>
> I'm picturing a pendulum that in its vertical position looks like this:
>
>  m2
>  ||
>  ||
>  ||
>  ||
>  xx
>  ||
>  ||
>  ||
>  ||
>  ||
>  ||
>  ||
>  ||
>  m