Question

Point masses 1, 2, 3 and 4 kg are lying at the points (0, 0, 0), (2, 0, 0), (0, 3, 0) and (-2, -2, 0) respectively. The moment of inertia of this system about X-axis will be

• A. $43kg{m}^2$
• B. $34kg{m}^2$
• C. $27kg{m}^2$
• D. $72kg{m}^2$

Answer 1

The correct option is A $43kg{m}^2$

Moment of inertia of the whole system about the axis of rotation will be equal to the sum of the moments of inertia of all the particles.

Moment of inertia $I=m{d}^2$

Moment of inertia about X-axis $=1kg\times 0^2+2kg\times 0^2+3kg\times 3^2+4kg{(-2)}^2=43kg{m}^2$