What does Young's modulus measure?

Young's modulus is a fundamental property of materials that quantifies their stiffness. It is defined as the ratio of stress (force per unit area) to strain (deformation relative to original size) within the linear elastic region of a material. This relationship allows engineers and designers to predict how much a material will deform under a given load.

When materials are subjected to tensile or compressive forces, Young's modulus helps in understanding how much they will stretch or compress. A higher Young's modulus indicates that a material is stiffer, meaning it deforms less under the same amount of stress compared to a material with a lower modulus. This property is crucial in applications where structural integrity and performance under loads are essential, such as in construction, automotive, and aerospace industries.

The other options do not accurately reflect what Young's modulus measures: hardness relates to resistance to indentation and scratching, resilience is about a material's ability to absorb energy and return to its original shape, and weight under stress pertains to the gravitational force acting on an object, which is unrelated to the elastic properties described by Young's modulus.