Final answer:
When the length of a runner's displacement and the distance traveled are the same, the runner's motion is uniform motion.
Step-by-step explanation:
When the length of a runner's displacement and the distance traveled are the same, the runner's motion is uniform motion. This means that the runner is moving with a constant velocity in a straight line.
For example, if a runner moves 5 meters in a straight line, then their displacement is also 5 meters, considering the initial position as 0 meters and taking the direction of motion as positive. In this case, the distance traveled is also 5 meters.
Therefore, when a runner's motion is uniform, their displacement and distance traveled will be the same.