Question

The radius of gyration of a body about an axis at a distance of $4cm$ from its centre of mass is $5cm$. The radius of gyration about a parallel axis through centre of mass is:

• A. $2cm$
• B. $5cm$
• C. $4cm$
• D. $3cm$

Answer 1

The correct option is D $3cm$

$m{r}_{gCM}^2+m{r}^2=m{r}_g^2$

$r_{gCM}^2+r^2=r_g^2$

$r_{gCM}^2+4^2=5^2$

$r_{gCM}=3cms$