Q 11-06-148JEE MainJEE Main 2021 (31 Aug, Shift 2)Easy
A system consists of two identical spheres each of mass $1.5$ kg and radius $50$ cm at the ends of a light rod. The distance between the centres of the two spheres is $5$ m. What will be the moment of inertia of the system about an axis perpendicular to the rod passing through its midpoint?
Answer: (C) $19.05\ \text{kg m}^2$
Each sphere (solid): $I = \dfrac25MR^2 + Md^2$ with $d = 2.5$ m.
$\dfrac25(1.5)(0.5)^2 = 0.15$ and $1.5\times(2.5)^2 = 9.375$.
$I_{\text{system}} = 2(0.15 + 9.375) = 19.05\ \text{kg m}^2$.
Solution by Sreeraj P, M.Sc Physics