Question

Two blocks of same mass 50 g are placed on a hanging rod in three different situations as shown in figure. Moment of inertia of the rod about axis of rotation is I₀ = 5000 g.cm². Find the moment of inertia of the system in each situation.

Answer 1

(a) I₁ = I₀ + mr₁² + m₂r₂²

= 5000 + 50 x (5)² + 50 x (5)²

= 5000 + 1250 + 1250

= 7500 g cm²

(b) I₂ = I₀ + m₁r₁² + m₂r₂²

= 5000 + 50 x (15)² + 50 x (15)²

= 5000 + 50 x 225 + 50 x 225

= 5000 + 11250 + 11250
= 27500 g cm²

(c) I₃ = I₀ + m₁r₁² + m₂r₂²

= 5000 + 50 x (30)² + 50 x (30)²

= 5000 + 50 x 900 + 50 x 900= 5000 + 45000 + 45000

= 95000 g cm²