Elasticity

A body can be deformed by applying the suitable force on it. After removing the force, if the body regains its original shape then it is perfectly elastic and this property is called elasticity. The property of a substance that makes it possible to change its length, volume, or shape in direct response to a force and to recover its original form upon the removal of a force. This restoring force is generally proportional to the amount of stretch, as described by Hooke's Law. Hooke's law states that, within the elastic limit the stress developed in the body is directly proportional to the strain produced in it. The maximum stress up to which a body exhibits the property of elasticity is called the elastic limit or limit of elasticity. Stress is the restoring or recovering force per unit area set up inside the body. It is the deforming force applied per unit area of the body. The three types of stress are: longitudinal stress, shearing stress, volume stress. Strain is the change in dimension of a body due to the deforming force. It is measured by the ratio of change in dimension to the original dimension. The three types of strain are linear strain, shearing strain and volume strain. There are three types of moduli of elasticity corresponding to three types of strains. They are Young's modulus of elasticity corresponding to linear strain or longitudinal strain, Rigidity modulus or shear modulus corresponding to shearing strain, and Bulk modulus or volume modulus corresponding to volume strain. Young's modulus of elasticity is, within the elastic limit, the ratio of longitudinal stress to longitudinal strain and is denoted by Y. Rigidity modulus is, within the elastic limit, the ratio of the tangential stress to the shearing strain and is denoted by n. Bulk modulus is, within the elastic limit of a body, the ratio of the volume stress to the volume strain and is denoted by K.