Re: [Phys-l] "compound" pendulum

[Stefan Jeglinski <jeglin@4pi.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.

Thanks for the tip. The reason I want to nail this down is exactly 
because I have an intro text that, while I'm not sure (yet) presents 
an incorrect analysis, at least misleads with a diagram.


> 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.

So granted. This sort of problem represents the typical limit to 
which I would try a force approach without switching over. But 
obviously my "force intuition" is lacking, so the pedagogy is pretty 
important, at least to me.


Stefan Jeglinski