Question

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 $3\stackrel{\circ }{A}$ then the inter atomic force constant :

• A. $5.4N/m$
• B. $7.5N/m$
• C. $7.6N/m$
• D. $30N/m$

Answer 1

The correct option is A $5.4N/m$

Young's modulus,

$Y=3K(1-2\sigma )=3\times {10}^{10}(1-2\times \sigma )=1.8\times {10}^{10}N/m^2$
∴ Inter atomic force constant is
$K=Yr=1.8\times {10}^{10}\times 3\times {10}^{-10}=5.4N/m$