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Welcome! Today we are going to explore kinematics—the science of how things move.
Kinematics is all about describing motion. We look at how fast things go, how far they travel, and which direction they are heading, without worrying yet about what forces caused them to move.
First, let's look at the difference between distance and displacement. Distance is the total ground you cover, while displacement is simply how far you end up from where you started, in a straight line.
Next, we have speed and velocity. Speed is just how fast you are moving (like 50 mph), but velocity is speed with a specific direction (like 50 mph North). We represent velocity with an arrow called a vector.
A track runner completes exactly one full lap around a circular 400-meter track, ending right where they started. What is their total distance traveled, and what is their final displacement?
- Identify the total ground covered to find the distance. Since the runner completed one full 400-meter loop, the total distance is 400 meters.
- Identify the starting point and the ending point to find the displacement.
- Because the runner ended at the exact same spot they started, the straight-line distance between their start and finish is zero.
- Therefore, the final displacement is 0 meters, even though the distance is 400 meters!
