What does the term 'strain' refer to in mechanics?

The term 'strain' in mechanics refers to the deformation of a material as a response to applied stress. It characterizes how much a material stretches, compresses, or otherwise deforms when subjected to an external force. Strain is typically expressed as a ratio or a percentage, which indicates the change in dimensions relative to the original dimensions of the material.

In the context of mechanics, an object experiences stress when an external force is applied, leading to internal forces within the material that attempt to maintain equilibrium. Strain occurs as a result of this stress, making it a direct measurement of the material's response to the applied load. This is critical in engineering to ensure designs can withstand the anticipated forces without failure. Understanding strain is essential for determining material behavior under load, which in turn informs the selection and safe use of materials in construction and other applications.

The other options refer to different concepts. Internal force pertains to the forces that develop within materials due to external loads but does not specifically define strain. Total energy within an elastic body describes the potential energy stored during deformation but is not synonymous with strain itself. The external load refers to the forces applied to an object, which lead to stress and, ultimately, to strain, but does not define the deformation