Consider a car that moves along a straight highway. When you first notice the car (from your helicopter high above), you turn on your stopwatch. The position of the car at this moment is 20 km south of Centretown, so we'll label this position $-20$ km. After 10 minutes, the car is 10 km south of Centretown, and after 20 minutes the car is at Centretown. After an additional 10 minutes, the car is 10 km north of Centretown, and the pattern continues for a while.

Describe the motion of the car, in every-day words, and using the technical language of physics.

Then sketch a position-time graph for the car, and use it to describe the motion in every-day words and in the technical language of physics.