Physics

Problem

When two rigid bodies are fastened together and rotate as a single object about the same fixed axis, the rotational inertia

I_{\text{total}}

of the combination is a) the arithmetic mean of the individual rotational inertias about that axis b)

\sqrt{I_1^{\,2}+I_2^{\,2}}

, the root-sum-of-squares of the individual rotational inertias c) the algebraic sum of the individual rotational inertias about that axis d)

\displaystyle \frac{I_1 I_2}{I_1+I_2}

, the product of the inertias divided by their sum