Interpreting Distance-Time Graphs

What does a line with no steepness on a distance-time graph indicate?

If a line on a distance-time graph has some steepness, what does it indicate about the object's speed?

In the first example, what is the direction of the object when it has constant speed?

In the second example, what does it mean if the line has no steepness?

In the second example, what is the direction of the object when it is moving with some steepness?

In the third example, what does a curved line on a distance-time graph indicate?

What does it mean if the steepness of a curved line on a distance-time graph increases?

What does it mean if the steepness of a curved line on a distance-time graph decreases?

In the third example, what is the direction of the object when it is speeding up?

In the third example, what is the direction of the object when it is slowing down?