Physics · Grades 6–9
Distance is not displacement
Use paths and signed positions to explain round trips.
Learn the idea
Path length
Distance is the total length travelled and is non-negative.
Change in position
Displacement is final position minus initial position and includes a direction or sign.
Round trips
Returning to the start makes displacement zero, but travelled distance need not be zero.
State the reference
Define your origin and positive direction before calculating signed displacement.
Worked examples
A learner walks 9 m east, then 4 m west on one line. Find total distance.
Distance adds both path lengths: 9 + 4 = 13 m.
13 m
For the same 9 m east and 4 m west trip, use east-positive. Find displacement.
Signed displacement is +9 − 4 = +5 m.
5 m
Check your understanding
A runner returns to the start after one complete lap. Which is zero?
- Elapsed time necessarily
- Displacement
- Distance travelled
On a signed axis, x changes from −6 m to +8 m. Find displacement.
Which quantity needs a direction or sign in one dimension?
- Elapsed time
- Displacement
- Distance
Answers and marking notes
Answers and marking notes
- Displacement
Final and initial positions coincide, so displacement is zero.
- 14 m
Subtract initial from final: 8 − (−6) = 14 m.
- Displacement
Displacement is a vector quantity, represented by a sign on a one-dimensional axis.
Further reading and review references
These are reference links, not copied exercises, institutional endorsement or proof of independent review.
Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.