Question

Moment of inertial of a disc about is own axis is $I$. Its moment of inertia about a tangential axis in its plane is

• A. $\frac{5}{2}I$
• B. $3I$
• C. $\frac{3}{2}I$
• D. $2I$

Answer 1

Answer: (A)

$\frac{5}{2}I$

$M.I.$ of disc about an axis passing through its COM and perpendicular to the plane is $I=\frac{1}{2}M{R}^2$
$M.I.$ of disc about its diameter is $I^{\prime }=\frac{M{R}^2}{4}=\frac{I}{2}$
$M.I.$ of disc about its tangential axis
$=\frac{I}{2}+M{R}^2=\frac{I}{2}+2I=\frac{5}{2}I$.