An elevator moving down passes its neighbor, an elevator moving up. Their speed relative to one another is 8 m/s. What is the velocity of each elevator relative to someone standing on the first floor? Assume that the elevators are traveling at the same speed, and that the upward direction is positive
4 m/s. If one elevator was moving at this speed independently, everything outside would be moving past at a speed of 4 m/s relative to the elevator. Add the other elevator moving past at 4 m/s, and it's relative speed to the other elevator is 8 m/s.
