Question

The moment of inertia of solid sphere is $20kg-m^2$ about the diameter. The moment of inertia about any tangent will be

• A. $70kg-m^2$
• B. $35kg-m^2$
• C. $50kg-m^2$
• D. $20kg-m^2$

Answer 1

The correct option is A $70kg-m^2$

$\frac{2}{5}m{R}^2=20$

About any tangent:

$\begin{array}{c}I=\frac{2}{5}m{R}^2+m{R}^2\\ =\frac{7}{5}m{R}^2\\ =\frac{7}{5}\times 50=70kg-m^2\end{array}$

$\therefore$ Option $A$ is correct.