Motion is everywhere around us. But how do we measure it? When an object moves from one place to another, we can describe this motion in different ways. Two fundamental concepts help us understand motion: distance and displacement. Distance measures the total path length traveled, while displacement measures the change in position from start to end point. Let's see how an object can move along different paths.
Distance is a fundamental concept in physics that measures the total length of the path traveled by an object. Unlike other quantities we'll explore later, distance is always positive and represents a scalar quantity, meaning it has magnitude but no direction. Distance is path-dependent, which means it accumulates as an object moves, regardless of the direction of motion. Watch as this car travels along a winding road - notice how the distance continuously increases as it follows every curve and turn of the path.
Displacement is fundamentally different from distance. While distance measures the total path traveled, displacement is a vector quantity that represents the change in position from the starting point to the ending point. Displacement has both magnitude and direction, and it's completely independent of the path taken. Notice how these two different paths result in exactly the same displacement vector - a straight arrow from start to finish. Displacement can be positive, negative, or even zero if an object returns to its starting position.
Now let's directly compare distance and displacement to understand their key differences. Distance is a scalar quantity with magnitude only, while displacement is a vector with both magnitude and direction. Distance is always positive and depends on the entire path traveled, whereas displacement can be positive, negative, or zero and only depends on the start and end positions. Watch this synchronized animation showing the same motion measured both ways - notice how distance continuously increases along the curved path, while displacement shows the straight-line change from start to current position.
Let's examine three practical examples to see how distance and displacement work in real situations. First, consider a student walking to school. Taking a direct route covers 800 meters, while going through the park covers 1200 meters. The distance differs, but the displacement is the same - 800 meters in the direction from home to school. Second, a runner completing one lap on a 400-meter circular track travels a distance of 400 meters, but the displacement is zero because they return to the starting point. Finally, a delivery truck making a round trip covers 15 kilometers in distance, but again has zero displacement since it returns to its origin.