I'm having some trouble prooving a basic compound pendulum theory - my company makes a piece of kit designed to do just that.(adsbygoogle = window.adsbygoogle || []).push({});

In a simple experiment involving a long thin bar which is set on a knife edge and allowed to swing freely I have been changing the length of the bar and measuring the time period.

The equation is tau = 2 pi * sqrt((k^2 + h^2) / g * h) designed to enable us to find a local estimate for g (gravity) and k - the radius of gyration of the rod. Plotting a graph and rearranging the eqn into y = mx + c gives an estimation of 9.84 for gravity (very good) and 0.268 for k.

The theory for k is simple, Rouths Rule states k^2 = (L^2) / 3. This gives k = 0.528.

Help. Have redone the expt over and over with increasing accuracy to no avail. Am confident that Rouths Rule holds as is 12.7mm diameter st/st rod with L = 915mm.

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# Compound Pendulum problem

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