Question

An elastic body is said to be isotropic if the elastic constants are ______

(a) same only in y- direction

(b) same only in x- direction

(c) different in al direction

(d) same in all direction

The question was asked in a national level competition.

I'm obligated to ask this question of Generalised Hooke’s Law topic in section Elements of Elasticity of Geotechnical Engineering I

Answer 1

The correct choice is (d) same in all direction

The best I can explain: When the elastic constants are same in all the direction at a point in a soil body, then the soil body is said to be isotropic. By considering the homogeneity and the isotropy, the number of elastic constants reduces to only two.