Figure two point three shows a worldline of a runner. The horizontal axis ranges from t equals zero to ninety seconds while the vertical axis ranges from x equal zero to 100 m. The runner is running between zero and eleven seconds. This portion of the graph is a straight line with positive slope. After eleven seconds, the runner is at the one hundred meter mark on the track. The runner is walking between eleven seconds and ninety-one seconds. This portion of the graph is a straight line with negative slope. After ninety-one seconds the runner is back to position zero, the starting line.