What is true regarding stress and strain in materials?

The chosen answer accurately describes the fundamental definitions of stress and strain in materials science. Stress is defined as the force applied to a material divided by the area over which that force is applied. This relationship is expressed mathematically as stress = force / area, which quantifies how much internal force a material experiences per unit area when subjected to an external load.

Strain, on the other hand, measures how much a material deforms in response to the applied stress. It is defined as the change in length (or extension) of a material divided by its original length. This relationship is expressed as strain = extension / original length, capturing the relative deformation of the material.

This understanding is essential for analyzing material behavior under different loads, predicting failure, and designing safe and effective structures and machines. The definitions in the selected answer align with standard engineering principles and are crucial for millwrights and other professionals in the field.