A delivery drone takes off vertically from a warehouse roof and travels 80 m due north, then 60 m due east, before hovering in position. Explain the difference between the total distance travelled by the drone and its displacement from the warehouse roof, and describe what is meant by each quantity.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A delivery drone travels 80 m due north and then 60 m due east from its starting point.
Model answer (5 marks)
Distance is the total length of the path travelled by the drone. The drone moves 80 m north and then 60 m east, so the total distance is 80 m + 60 m = 140 m. Displacement is the straight‑line distance from the starting point to the finishing point, in a specified direction. It is a vector quantity, having both magnitude and direction, whereas distance is a scalar quantity with magnitude only. The displacement of the drone is the hypotenuse of the right‑angled triangle formed by the 80 m north and 60 m east legs, i.e. √(80²+60²)=100 m, which is less than the total distance of 140 m.
Examiner tips
- State the definitions of distance and displacement first.
- Give the numerical values (140 m and 100 m) and show the calculation for displacement.
- Mention that distance is scalar and displacement is a vector.
Common mistakes
- Confusing distance with displacement or vice versa.
- Omitting the direction in the description of displacement.
- Failing to calculate the displacement using Pythagoras’ theorem.
Mark scheme (5 marks)
- Distance is the total length of the path travelled by the drone
- Total distance = 80 m + 60 m = 140 m
- Displacement is the straight-line distance from the starting point to the finishing point (in a specified direction)
- Displacement is a vector quantity / has both magnitude and direction, whereas distance is a scalar quantity / has magnitude only
- The displacement of the drone is 100 m (north-east / at an angle from the warehouse roof), which is less than the total distance of 140 m
Key terms in this question
Related
- All WJEC A-Level Physics (Wales) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Basic physics quantities and motion questions
- A student states: 'Speed and velocity are the same thing.' Explain why this stat…
- A student is timing a remote-controlled car as it moves along a straight road. T…
- A sprinter runs 100 m along a straight track in 12.5 s, then immediately turns a…
- A cyclist travels 12 km due north to reach a town, then immediately turns around…