The mass moment of inertia of a cube with edges of length b, about an axis passing through an edge
- A. $mb²/2$
- B. $mb²/6$
- C. $2mb^2/3$
- D. $2mb^2/3$
Answer: C. $2mb^2/3$
Explanation: Using parallel axis theorem. $I_{cm} = m(b²+b²)/12 = mb²/6$. Distance to edge $d = b/\sqrt{2}$. $I_{edge} = mb²/6 + m(b²/2) = 4mb^2/6 = 2/3 mb²$.