Ball-on-Ball action

foreach (Ball ball in balls)
            {
                foreach (Ball otherBall in balls)
                {
                    if (ball != otherBall)
                    {
                        // TODO: Put your collision handling with another ball code here
                        if (ball.BoundingSphere.Intersects(otherBall.BoundingSphere))
                        {
                            Console.WriteLine("Ball/ball collision");

                            Vector3 difference = otherBall.Position - ball.Position;    // get vector between 2 ball centers

                            // calculate vector components
                            difference.Normalize();
                            float a1 = Vector3.Dot(ball.Velocity, difference);
                            float a2 = Vector3.Dot(otherBall.Velocity, difference);

                            // using radius as mass, make the equations play nice
                            float p = (2 * (a1 - a2)) / (ball.BoundingSphere.Radius + otherBall.BoundingSphere.Radius);

                            ball.Velocity = ball.Velocity - p * otherBall.BoundingSphere.Radius * difference;
                            otherBall.Velocity = otherBall.Velocity + p * ball.BoundingSphere.Radius * difference;
                        }
                    }
                }
            }