Which of the following potential energy curves in figure., cannot possibley describly describe the elastic collision of two billiard balls ? Here r is distance between centres of the balls.

Explanation

The potential energy of a system of two masses varies inveresly as the distance ® between them, i.e., `V(r)prop(1)/(r)`. When the twor billiard balls touch eachother,P.E. becomes zero i.e. at `r=R+R=2R,V(r )=0`. Out of the given curve (v) only satisfies these two conditions. Therefore, all other curves cannot possibly describe the elastic collision of two biliard balls.