To draw a displacement vector to the third time interval, you need to draw an arrow from the starting point to the fourth dot. In other words, you DO NOT count dots as time intervals. Each GAP between dots is a time interval!

An arrow through the first four dots, pointing to the right.

The displacement between each pair of dots is represented by an arrow. Since he’s going from home to school, all the arrows are pointing to the right.

Arrows between each dots, all pointing right.

Even though the two students observed the same object, their position vectors were not the same because the origins they set for their motion diagrams were not the same.

Take the diagram for Problem 6 as an example. If home was on the right and school was on the left of the picture, the origin would be in a different position than in that problem. The position vector from home to school would point in the opposite directions too.

Their origins were different.

This question tests your understanding of position, displacement, and distance within a time interval.

The two students mentioned would agree on the displacement, distance, and time interval for the trip.

The displacement, or how far an object has moved from the origin to the final point, will be the same in both cases.

The distance from the grocery store to the post office will be the same in both cases as well.

The amount of time it took to go from the grocery store to the post office will stay in the same in both cases.

However, the positions will NOT be agreed on. Position is measured from the origin of a coordinate system to where the object is. Essentially, the friend will be dealing with negative values for position in his/her coordinate system.

Agrees on distance, displacement, and time. Disagrees on position.