\f1) A ball thrown upward and a ball thrown downward at the same time with the same initial speed. 2) A race car speeding up to match the speed of a second race car. 3) A car, initially at rest, accelerating and a car moving initially at constant speed applying the brakes until it stops. 4) An initially moving truck speeding up eastward and a westward moving truck slowing down. 5) A car moving at a steady speed is overtaken by a police car starting from rest. 6) A train, initially moving at a steady speed, has brakes applied to match the speed of a train on a parallel track