What is the total displacement of a dog that runs north 80 meters to chase a ball, returns to its master, and then runs south 20 meters? 60 meters 80 meters 20 meters 100 meters

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:

which means that the displacement is 20 meters in the south direction.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.