The potential energy U of diatomic molecules as a function of separation `r` is shown in figure. Identify the correct stateement.

Options

A. The atoms are in equilibrium if `r = OA`
B. The force is repulsive only if `r` lies between A and B
C. The force is attractive if `r` lies between A and B
D. The atoms are in equilibrium if `r =OB`

Answer

D

Explanation

`F = - (dU)/(dr)` = - slope of U - r graph
At B, `"slope" = 0 `
`:. F = 0`
Hence , atoms are in equilibrium at B. From A to B or even before A slope is negative . Hence , force is positive force mean repulsion.