Answer:
20 meters
Explanation:
The displacement of an object is a vector whose magnitude is equal to the distance between the final point of the motion and the starting point.
In this problem:
- the dog starts from its master position
- it runs 80 meters north
- it runs 80 meters south
- it runs 20 meters south
So, its final position (and so, its displacement) is 20 meters south, since after the first two motions, it came back to its original position. In other words:
[tex]d= + 80 - 80 - 20 = -20[/tex]
which means that the displacement is 20 meters in the south direction.
