Final answer:
John's displacement is 0 m because he returned to his starting point, resulting in no net change in position, despite walking a total distance of 4m.
Step-by-step explanation:
John walks 2m to the store and then walks 2m back home. His displacement, which is a vector quantity representing the shortest distance from his initial to his final position, is 0 m. This is because displacement takes into account the direction of the motion, and since John returns to his starting point, there is no net change in position. Despite walking a total distance of 4m (2m out and 2m back), displacement is concerned only with the overall change in position.