Question

Find the MOI of a uniform circular disc of mass $M=10\text{kg}$ and radius $R=10\text{m}$ about tangent perpendicular to its plane.

• A. $1200{\text{kg m}}^2$
• B. $1500{\text{kg m}}^2$
• C. $1400{\text{kg m}}^2$
• D. $1000{\text{kg m}}^2$

Answer 1

The correct option is B $1500{\text{kg m}}^2$

Given, $M=10\text{kg}$, $R=10\text{m}$
MOI about COM of the disc is
$I_{COM}=\frac{1}{2}M{R}^2$


From parallel axis theorem, MOI about tangent perpendicular to plane of disc is
$I=I_{COM}+M{d}^2$
Here, $d=R$
$\therefore I=\frac{1}{2}M{R}^2+M{R}^2$
$\Rightarrow I=\frac{3}{2}M{R}^2=\frac{3}{2}\times 10\times {10}^2$
$\Rightarrow I=1500{\text{kg m}}^2$