Question

A disc of mass $M$ and radius $R$ is rotating about one of its diameter. The value of radius of gyration for the disc is

• A. $R/4$
• B. $R/2$
• C. $R/6$
• D. None of these

Answer 1

Answer: (B)

$I_{\text{ disc}}$ about the axis along its diameter
$=\frac{M{R}^2}{4}$ ...(i)
Using radius of gyration, $I=M{k}^2$ ...(ii)
Comparing Eqs. (i) and (ii), we get $k=\frac{R}{2}$.