JEE Main & Advanced Physics Elasticity Interatomic Force Constant

Behaviour of solids with respect to external forces is such that if their atoms are connected to springs. When an external force is applied on a solid, this distance between its atoms changes and interatomic force works to restore the original dimension.

The ratio of interatomic force to that of change in interatomic distance is defined as the interatomic force constant.

\[K=\frac{F}{\Delta r}\]

It is also given by \[K=Y\times {{r}_{0}}\] [Where \[Y\]= Young's modulus, \[{{r}_{0}}=\] Normal distance between the atoms of wire]

Unit of interatomic force constant is N/m and Dimension \[M{{T}^{-2}}\]

Note :

• The number of atoms having interatomic distance \[{{r}_{0}}\] in length \[l\] of a wire, \[N=l/{{r}_{0}}\].

The number of atoms in area A of wire having interatomic separation \[{{r}_{0}}\] is \[N=A/r_{0}^{2}\].