Question

Three-point masses m each are located at the vertices of an equilateral triangle. What is the moment of inertia of this system about an altitude of the triangle passing through the vertex, if ‘a’ is the size of each side of the triangle ?

(a) ma²/2 (b) 3m a² (c) m a² (d) 3/4ma²

Answer 1

Correct option (a) ma²/2

Explanation:

We have

I = I₁ (m at A) + I₂ (m at B) + I₃ (m at C) 

 = m x 0² + m x (a/2)² + m (a/2)² 

 = ma² /2