Note return — FOOTNOTES

If no external forces act upon a body its particles assume certain relative positions, and it has what is called its natural shape and size. If sufficient external force is applied the natural shape and size will be changed. This distortion or deformation of the material is known as the strain. Every stress produces a corresponding strain, and within a certain limit (see elastic limit, page 5) the strain is directly proportional to the stress producing it.1 The same intensity of stress, however, does not produce the same strain in different materials or in different qualities of the same material. No strain would be produced in a perfectly rigid body, but such is not known to exist.