is removed, interatomic forces of attraction or repulsion restore the atoms to their equilibrium positions. If a body regains its original shape and size after the removal of deforming force, it is said to be elastic and the property is called elasticity . The force which changes the size or shape of a body is called a deforming force. Examples: Rubber, metals, steel ropes.
Figure . Elasticity Plasticity: If a body does not regain its original shape and size after removal of the deforming force, it is said to be a plastic body and the property is called plasticity. Example : Glass . .
Stress and strain (a) Stress: When a force is applied, the size or shape or both may change due to the change in relative positions of atoms or molecules. This deformation may not be noticeable to Figure . Schematic representations of the transition from solid to liquid to gaseous states with a change in external energy Energy Gas Liquid Solid In addition to the three physical states of matter (solid, liquid, and gas), in extreme environments, matter can exist in other states such as plasma, Bose-Einstein condensates. Additional states, such as quark-gluon plasmas are also believed to be possible.
A major part of the atomic matter of the universe is hot plasma in the form of rarefied interstellar medium and dense stars. In the study of Newtonian mechanics (Volume ), we assumed the objects to be either as point masses or perfect rigid bodies (collection of point masses). Both these are idealized models. In rigid bodies, changes in the shape of the bodies are so small that they are neglected.
In real materials, when a force is applied on the objects, there could be some deformations due to the applied force. It is very important to know how materials behave when a deforming force is applied. - - - - Unit Properties of matter Similarly, the tangential stress or shearing stress σ t over the area is defined as σ t t F = ∆ Longitudinal stress can be classified into