Stiffness of an elastic body with a single degree of freedom

Description

The stiffness of a body is a measure of the resistance offered by an elastic body to deformation. For an elastic body with a single degree of freedom (for example, stretching or compression of a rod), the stiffness is depended on the force applied on the body and the displacement produced by the force.
(The degree of freedom (DOF) of a mechanical system is the number of independent parameters that define its configuration.)