Question

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?


100 meters

60 meters

80 meters

20 meters

Answer 1

To find the total displacement of the dog, we need to consider the overall change in position from its starting point.

1. The dog runs north 80 meters.
2. Then it returns to its master, which means it goes back 80 meters to the starting point (net change = 0).
3. Finally, the dog runs south 20 meters.

Now we can calculate the total displacement:

- From the starting point, after running north 80 meters, the dog is at +80 meters.
- Then returning to the master puts it back at 0 meters.
- Running south 20 meters from there brings it to -20 meters.

The total displacement is the final position relative to the original starting point:

\[
\text{Total Displacement} = 0 - (-20) = -20 \text{ meters} \text{ (south)}
\]

In terms of magnitude, the total displacement is 20 meters south.

So, the correct answer is:

**20 meters**.