The moment of inertia of a solid sphere of mass $M$ and radius $R$ about a diameter is:
A$\dfrac{1}{2}MR^2$
B$\dfrac{2}{3}MR^2$
C$\dfrac{2}{5}MR^2$
D$MR^2$
Answer & Solution
Correct answer: C. $\dfrac{2}{5}MR^2$
Standard result for a solid sphere about a central axis: $I = \dfrac{2}{5}MR^2$. Compare with a hollow (thin-shell) sphere where $I = \dfrac{2}{3}MR^2$ — that's option D and a common trap.
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