Q. Between stress and strain, which is the cause and which is the result? And why?
Ans. When a deforming force is applied on a body, it changes the configuration of the body by changing the normal position of the molecules or atoms of the body. As a result, an internal restoring force comes into play which tends to bring the body back to its initial configuration. This internal restoring force acting per unit area of a deformed body is called stress. When a deforming force is applied on a body, a change occurs in the configuration of the body and the body is said to be strained or deformed. The ratio of change in configuration to the original configuration is called strain.
Strain causes a stress in the body, so we can say that strain is the cause and stress is its result.