The change in the volume to original volume (V) is called
Note: It is obvious from
the above definition of Strain, that Strain is just a number without a unit.
The measure of resistance to deformation is called stress.
The following stresses corresponding to each type of deformation can be defined.
Longitudinal or Tensile Stress
The restoring forces per unit normal cross-sectional area is
called the tensile stress.
Click here to enlarge
The restoring force, per unit lateral area, is called shear stress.
The restoring force per unit normal area of the surface is called bulk stress.
Since Pressure = Force / Normal Area
Note : The stress is measured in the unit of Newton/(meter)2 i.e., N/m2.