Final answer:
To represent motion in the negative direction, a position vs. time graph slopes downwards as time increases, while a velocity vs. time graph shows a horizontal line in the negative velocity region, where the shaded area represents displacement.
Step-by-step explanation:
When analyzing motion, it is essential to understand that the direction we consider positive or negative is arbitrary and depends on the coordinate system we choose. For telling the motion's direction, the position vs. time and velocity vs. time graphs are very informative.
Position vs. Time Graph
If the motion of an object is in the negative direction, the position-time graph would show a line that slopes downwards as time progresses. This indicates that as time increases, the position is becoming more negative, suggesting that the object is moving away from the origin in the direction we've defined as negative.
Velocity vs. Time Graph
A constant negative velocity would be represented by a horizontal line located in the negative portion of the velocity axis on a velocity vs. time graph. The area under this line and above the time-axis (which could be shaded) represents the object's displacement over a given time period.