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 inversely as the distance(r) between 1
them, i.e., `V(r)alpha 1//r`. When the two billard touch each other, P.E. Becomes zero i.e.,at r=R+R=2R, V(r) =0. Out of the given graphs, curve (v) only satisfies these two condition. Therefore, all other curves cannot possibly describe the eleastic collision of two billiard balls.