Author: Dr. Donald Luttermoser of East Tennessee State University III. Motion in One Dimension A. Displacement. 1. The displacement of an object is defined as the change in its position. 2. It is given by the difference between its final and initial coordinates: x xf − xi = displacement. (III-1) 3. Displacement is a vector quantity =) has direction and magnitude: ~x ~xf − ~xi . (III-2) Example III–1. A car starts at a position 30 m from a stop sign and continues past the stop sign until it comes to rest 120 m past the sign. What is its displacement?