Two identical balls bearing in contact with each other and resting on a frictionless table are hit head on by another ball bearing the same mass moving initially with a speed v as shown in figure. If the collision is elastic, which of the following (figure) is a possible result after collision? [NCERT Exemplar]

When two bodies of equal masses collide elastically, their velocities are interchanged.

When ball 1 collides with ball 2, then velocity of ball 1, v₁
becomes zero and velocity of ball 2, v₂ becomes v, i.e.
                          v₁ = 0  and v₂ = v
Similarly, when ball 2 collides with ball 3 , v₂ = 0 and v₃ = v.

Also in elastic collision both momentum and energy remain conserved .
Hence, figure (2) is correct.