In a perfectly elastic collision in a two body system, relative to the center of momentum frame, the absolute magnitude of momentum (and velocity) of each object is retained by that same object.
In an oblique collision of two spheres, relative to the center of momentum frame, a line intersecting the center of both spheres, the center of momentum, and the point of contact will exactly bisect, in the same plane, the angle between the direction a sphere came from, and the resulting direction of travel of that sphere.
