Final answer:
The deformation experienced by a rectangular plate under stress is shear deformation, characterized by the parallel shift of material layers due to tangentially applied antiparallel forces.
Step-by-step explanation:
The deformation experienced by a rectangular plate under stress described in your question refers to shear deformation. When shear stress is applied to a material, such as a rectangular plate, two antiparallel forces of equal magnitude are acted tangentially on opposite surfaces. This results in a sideways deformation, where layers of the material shift parallel to the force applied. The measure of this deformation is the shear strain, which is the ratio of the displacement (Δx) of the layers in the direction of the forces to the original transverse length (Lo) of the material. The expression for shear deformation is Δx = FLo / SA, where F is the force applied, S is the shear modulus of the material, A is the area to which the force is applied, and Lo is the original transverse length.