Question

The radius of gyration of a circular disc of mass $m$ rotating about an axis perpendicular to its plane and passing through the center is:

• A. $2R$
• B. $1.4R$
• C. $R/1.4$
• D. $R/2$

Answer 1

The correct option is C $R/1.4$

$I_0=\frac{M{R}^2}{2}$
$K=$ radius of gyration

$K=\sqrt{\frac{I}{M}}$

$K=\frac{1}{\sqrt{2}}R$

$K\approx \frac{R}{1.4}$