A steel bar is held by two fixed supports as shown in the figure and is subjected to an increases of temperature $$\Delta T = {100^ \circ }C.$$ If the coefficient of thermal expansion and Young's modulus of elasticity of steel are $$11 \times {10^{ - 6}}/{}^ \circ C$$ and $$200$$GPa, respectively, the magnitude of thermal stress (in MPa) induced in the bar is __________.

A rod is subjected to an uniaxial load within linear elastic limit. When the change in the stress is $$200$$ MPa, the change in the strain is $$0.001.$$ If the Poisson's ratio of the rod is $$0.3$$ the modulus of rigidity (in GPa) is ________ .

If the Poisson's ratio of an elastic material is $$0.4$$, the ratio of modulus of rigidity to Young's modulus is _____ .

The number of independent elastic constants required to define the stress-strain relationship for an isotropic elastic solid is ________