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The moment of inertia of a hollow cubical box of mass M and side length a , about an axis passing through centres of two opposite faces, is equal to x M a 2 18 . The value of x is

Correct answer

5

Step-by-step solution

Let m be the mass of each face of the cubical box. I = 2 × m a 2 6 + 4 × m a 2 12 + m a 2 2 = 5 m a 2 3 But, m = M 6 ∴ I = 5 M a 2 18 ⇒ x = 5

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