The graph above plots the journey of a car. Section A
shows the car moving away from the start at a
constant speed (the straight positive gradient
line indicates constant speed where the distance
is increasing in proportion to the time)
In section B the time is increasing but the distance
is not increasing (flat line). This means that the car
is not moving. In section C there is a straight
line with a negative gradient. This sows that the
car is returning the the start at a constant speed.