# The physical pendulum - mass calculations

1. Aug 16, 2013

### HalcyonicBlues

When analysing the forces/energy transfers acting on a physical pendulum (albeit with a larger mass on the end, such as a grandfather clock...with a thick rod?) is it absolutely necessary to know the mass of the 'arm' (separate from the bob, as such)? Also, can the mass of the arm be calculated (or at least estimated) if the period, length of the arm and mass of the bob are known?

2. Aug 16, 2013

### voko

It is not the mass that you really need to know, but the moment of inertia.

3. Aug 16, 2013

### haruspex

Certainly, if you assume the arm is uniform and the bob is small enough to treat as a point (or has a calculable MI).