Question

The potential energy U between two molecules as a function of the distance x between them has been shown in the figure. The two molecules are. 

(A) Attracted when x lies between A & B and are repelled when x lies between B & C. 

(B) Attracted when x lies between B and C and are repelled when x lies between A and B. 

(C) Attracted when they reach B. 

(D) Repelled when they reach B.

Answer 1

Correct option: (B) Attracted when x lies between B and C and are repelled when x lies between A and B.

Explanation:

F = – (dU / dx)

In the region BC slope of graph is positive i.e. (dU / dx) = positive

F = – (dU / dx) = negative meaning force is attractive in the region AB, slope of graph is negative

F = – (dU / dx) = positive meaning for is repulsive

∴ when x is between BC, Force is attractive and it is repulsive when x is between AB.