Final answer:
The side length of the square is 12 cm.
Step-by-step explanation:
To find the side length of the square, we need to find the square root of the area given. A stationary particle has a world line that is a vertical line parallel to the time axis, while the world line for a particle with constant velocity is a straight line inclined to the time axis. When considering a velocity vs. time graph, a horizontal line represents a constant velocity. The area under such a graph can be used to calculate the displacement of the particle over a given period. The square root of 144 cm² is 12 cm. Therefore, the side length of the square is 12 cm.