Coordinate Systems
Because a difference in position is required when employing the Law of Change for the One-Dimensional Motion with Constant Velocity model, it is important to carefully consider the problem statement, define a useful coordinate system and accurately assign the initial and final positions. The arbitrariness of choice of origin and direction in the selection of coordinates is a powerful feature of all the motion models, but it is important to remember that with great power comes great responsibility: failing to consider your coordinate system can lead to sloppy math.
Check your understanding by solving this Milestone Problem:
Overdriving Headlights (How long can you drive at constant velocity before you have to hit the brakes, assuming standard night detection distances?)