Distance vs Displacement
This is a simple physics tutorial aimed at high school students in grades 9 and 10 (GCSE, HSC) answering the common questions:
- What is distance?
- What is displacement?
- How do distance and displacement differ or compare?
This tutorial is a follow on from one reviewing scalar and vector measurements.
What is Distance?
Distance is a measure of how far an object has moved. It is a scalar quantity, so it only gives you the magnitude of the journey, and not direction. For example, you can describe the distance traveled by the below biker simply as 10km. No other information is necessary to describe the distance covered in the journey.
What is Displacement?
Displacement is also a measure of how far an object has moved, but it is a vector measurement. What does this mean? It means that it gives both magnitude and direction. For example, you can describe the displacement of the biker in the image above as 10km to the East (or to the right) of its point of origin.
The direction is an essential component of describing the displacement of the biker. Without it, all you will have described is distance, not displacement.
How else do distance and displacement differ?
Although both distance and displacement both describe the magnitude of a journey, they differ in the way they measure this.
The video above goes through three examples, and demonstrates how distance and displacement are measured, and how they compare. You'll see that in practical terms, the displacement of an object is measured in a straight line from the starting point to the end point.
The last example in the video reviews the distance and the displacement of the earth after one orbit around the sun. This example demonstrates that if the origin and the destination are the same, the displacement will be zero.