The Poisson's ratio for a perfectly incompressible linear elastic material 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 ________ .

A steel cube, with all faces free to deform, has Young’s modulus, $$E,$$ Poisson’s ratio, $$ν,$$ and coefficient of thermal expansion, $$\alpha .$$ The pressure (hydrostatic stress) developed within the cube, when it is subjected to a uniform increase in temperature, $$\Delta T,$$ is given by

A metallic rod of $$500$$mm length and $$50$$mm diameter, when subjected to a tensile force of $$100$$kN at the ends, experiences an increase in its length by $$0.5$$mm and a reduction in its diameter by $$0.015$$mm. The Poisson's ratio of the rod material is _______ .