MCQ
In a rectangle $ABCD\,\,(BC = 2AB)$. The moment of inertia along which axis will be minimum
  • A
    $BC$
  • B
    $BD$
  • C
    $HF$
  • $EG$

Answer

Correct option: D.
$EG$
d
The moment of inertia will be minimum about that axis, which is passing through the center of mass.

$I_{E G}=\frac{M B^{2}}{12}$

$I_{F H}=\frac{M(2 B)^{2}}{12}=\frac{M B^{2}}{6}$

$M. I.$ of the rectangular plate about its diagonal $I_{B D}=\frac{M B^{2} L^{2}}{6\left(B^{2}+L^{2}\right)}=\frac{M B^{2} \times 4 B^{2}}{6\left(B^{2}+4 B^{2}\right)}=\frac{2}{15} M B^{2}=\frac{M B^{2}}{7.5}$

$M. I.$ about $E G$ is minimum.

$\mathrm{OR}$

By observation, distribution of mass is the nearest about axis $E G .$

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