Question

A solid Aluminium sphere of radius $R$ has moment of inertia I about an axis through its center. What will the moment of inertia about a central axis of a solid aluminium sphere of radius $2R$?

• A. $8I$
• B. $32I$
• C. $4I$
• D. $16I$

Answer 1

The correct option is B $32I$

The sphere of twice the radius has eight times the volume and eight times the mass,
Since, $V=\frac{4}{3}\pi r^3$
and the $r^2$ term in $I=\frac{2}{5}m{r}^2$ also becomes four times larger.

Final Answer: (d)