Kinematics · 18 min
Distance & Displacement
Two runners, two totals — only one of them cares which way you're facing.
Why should I care?
A runner does one full lap of a 400 m track. How far have they travelled?
Most people answer 400 m — and for distance, that's right. But ask where they ended up relative to where they started, and the answer changes completely. That gap between 'how far' and 'how far from start' is the whole idea behind this lesson.
Explore
Plot the path
Drag the runner along the track below. Watch how total distance climbs steadily while displacement swings back toward zero as they return to the start.
The idea
Two ways to measure motion
Distance is the total length of the path travelled — it only ever adds up, never cancels out. Displacement is the straight-line change in position from start to finish, and it has direction. A lap that ends where it started has covered real distance but zero displacement.
True or false?
If displacement is zero, the object didn't move.
Worked example
Worked example
A cyclist rides 300 m east, then 120 m west. Find the total distance and the displacement.
- 1
Distance ignores direction — add both legs.
Your turn
A student walks 8 m north then 8 m south. What is their displacement?