Question

Four masses are fixed on a massless rod as shown in the adjoining figure. The moment of inertia about the dotted axis is about(a) 2 kg × m²(b) 1 kg × m²(c) 0.5 kg × m²(d) 0.3 kg × m²

Answer 1

Moment of inertia = m1r1² + m2r2² + .............. mn²rn²

moi = 5*.2² + 2*.4² + 5*.2² + 2*.4²

=> 1 kg m²

Answer 2

Answer:

b) 1 kg × m²

Explanation:

Total number of masses = 4 (Given)

Weight one = 2kg (Given)

Weight two = 5kg  (Given)

Length one  = 0.2m  (Given)

Length two = 0.4m  (Given)

Moment of inertia = m × r²

Where the chosen origin is at the point through which the axis passes the rod. Thus, according to the formula -  

The total moment of inertia about the axis will be -

= 2 × W1 × L1² + 2 × W2 + L2²

= 2 ×5 × (.2)² +2× 2 × (.4)²

= 1.04 kgm²

Therefore, the moment of inertia about the dotted axis is about 1 kg × m².