Q: Three identical thin rods, each of mass m and length *l*, are joined to form an equilateral triangular frame. The moment of inertia of the frame about an axis parallel to its one side and passing through the opposite vertex and its radius of gyration about the given axis respectively are

(a) $ \displaystyle \frac{3}{2} m l^2 , l \sqrt{\frac{5}{12}}$

(b) $\displaystyle \frac{3}{4} m l^2 , l \sqrt{\frac{5}{12}}$

(c) $ \displaystyle 3m l^2 , l \sqrt{\frac{12}{5}}$

(d) $ \displaystyle \frac{1}{2} m l^2 , l \sqrt{\frac{12}{5}}$

Ans: (b)