Q. 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 $A$ and $B$ and are repelled when $X$ lies between $B$ and $C$
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 $B$
Explanation
(b) $F = - \left( \frac{dU}{dx} \right)$
In the region $BC$ slope of the graph is positive
$\therefore F =$ negative $i.e.$ force is attractive in nature
In the region $AB$ slope of the graph is negative
$\therefore F =$ positive $i.e.$ force is repulsive in nature
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.