The bulk modulus of a metal is ${10}^{10} N/m^2$ and Poisson’s ratio 0.20. If average distance between the molecules is$3A^0$ then the interatomic force constant is          

The relation between bulk modulus K, Poisson’s ratio $\sigma$ and Young’s modulus Y is

$Y=3K(1-2\sigma )$

Given, $K={10}^{10}(1-2\times 0.2)$

$\therefore Y=3\times {10}^{10}(1-2\times 0.2)$

$=1.8\times {10}^{10}N/m^2$

Interatomic force constant is

$K=yr=1.8\times {10}^{10}\times 3\times {10}^{-10}$

$K=5.4 N/m$