A girl leaves a history classroom and walks 10. meters north to a drinking fountain. Then she turns and walks 30. meters south to an art classroom. What is the girl's total displacement from the history classroom to the art classroom?
20. m south
20. m north
40. m north
40. m south
A car travels 20. meters east in 1.0 second. The displacement of the car at the end of this 1.0-second interval is