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Compound and simple pendulum, help asap

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1. Revising for an upcoming exam and came across this Q
A simple pendulum follows the proportionality of T^2 proportional to L, explain why it isn't the case with a compound pendulum.

Any ideas??
2. (Original post by pleasehelp1)
Revising for an upcoming exam and came across this Q
A simple pendulum follows the proportionality of T^2 proportional to L, explain why it isn't the case with a compound pendulum.

Any ideas??
With a simple pendulum the distance from the pivot to the centre of mass is exactly the length L as it consists of just a bob on a string. With a compound pendulum, i.e. a rod, the centre of mass will be at the centre of the rod (providing uniform mass distribution) and the pivot won't be at the end of the rod. This means the distance between the pivot point and the centre of mass won't be L. When actually doing the problem you have to take into account the moment of inertia of the rod but what I said above should be alright for an A-level question.

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