Simple Stress and Strain MCQ with answer and solution

Concept

Poisson's ratio is lateral strain divided by linear (longitudinal) strain.

Formula

μ = lateral strain / linear strain

Step-by-step solution

1. When a bar is pulled, its length increases. This is linear (longitudinal) strain. 2. At the same time, its width decreases. This is lateral strain. 3. The ratio of lateral strain to linear strain is called Poisson's ratio (μ or ν). 4. Answer is (D).

Explanation

When we stretch a bar, it becomes longer and thinner at the same time. The ratio of the change in width (lateral strain) to the change in length (linear strain) is Poisson's ratio. Its value lies between 0 and 0.5.

Why the other options are wrong

A: Young's modulus = normal stress / normal strain. B: Modulus of rigidity = shear stress / shear strain. C: Bulk modulus = direct stress / volumetric strain.

Shortcut

Strain divided by strain gives Poisson's ratio. Stress divided by strain gives a modulus.

Common mistake

Taking the ratio upside down (linear / lateral), or confusing it with a modulus.