= Finite-radius spherical pendulum bob
{title2=$T=2\pi\sqrt{(L^2+2a^2/5)/(gL)}$}
A homogeneous spherical bob rigidly fixed to a massless support has centre-of-mass distance $L$ from its pivot and intrinsic <moment of inertia> $2Ma^2/5$. The <parallel axis theorem> and linear gravitational restoring <torque> give the title <period> for small <oscillations>. Relative to a <point mass> at the same centre, the leading fractional <period> increase is $a^2/(5L^2)$. If $L$ is instead measured to the <sphere>'s surface, the centre distance must first be changed to $L+a$.
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