What is the displacement for a driver who travels 10 km to get to a point that is 4 km from his starting point?

4 Km

Explanation:

Displacement is 4 Km because it only refers to the object´s initial and final position, for example if the object returns to the same position from which it left, its displacement is zero. In this case the object´s initial position is zero and its final position is 4, then the difference of final and initial point is (4 Km – 0 Km)= 4 Km

Displacement is defined as the change in position, the displacement horizontal can be called Δx, then is a net change, and it differs in magnitude from total distance traveled.

one would be wind another would be water density