In a head on elastic collision of two bodies of equal masses

In head on elastic collision of two bodies of equal masses, it is not possible :

. During head on elastic collision, two bodies of masses m_(1) and m_(2) completely exchange their velocities when

Consider the elastic collision f two bodies A and B of equal mass. Initially B is at rest and A moves with velocity v . After the collision -

Consider the elastic collision f two bodies A and B of equal mass. Initially B is at rest and A moves with velocity v . After the collision -

Show that in two demensional elastic I collision between two bodies of equal mass and one body initialy at rest, they move at an angle of frac(pi)(2) after collision.