Question

Q1: What is the difference between distance and displacement?

Answer 1

Distance is a scalar quantity that measures the total length of the path traveled (always nonnegative).
Displacement is a vector quantity that gives the straight-line change in position from the initial point to the final point; it has both magnitude and direction.

Key differences
- Scalar vs vector: distance has only magnitude; displacement has magnitude and direction.
- Path dependence: distance depends on the actual path taken; displacement depends only on the initial and final positions.
- Relation: |displacement| ≤ distance, with equality only when motion is along a straight line in one direction.
- Examples: walk 3 m east then 4 m west → distance = 7 m, displacement = 1 m west. Walk 3 m east then 3 m back → distance = 6 m, displacement = 0.
- Formula: displacement = r_final − r_initial (vector).
- Related kinematics: average speed = total distance / time, average velocity = displacement / time.

Units for both are the same (e.g., meters).