Question

A person swims to the other end of a 20m long pol and back. What is their displacement?

Answer 1

Distance is a scalar quantity that refers to "how much ground an object has covered" during its motion. BUT Displacement is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position.  so here distance is 40 m but displacement is obviously zero meter.  so answer is 0  more information on: https://www.physicsclassroom.com/class/1DKin/Lesson-1/Distance-and-Displacement