AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Students should be able to explain the vector–scalar distinction as it…
Full specification wording
Velocity: Students should be able to explain the vector–scalar distinction as it applies to displacement, distance, velocity and speed.
Distance and speed are scalar quantities: they record magnitude only.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 2 of 3
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Distance and speed are scalar quantities: they record magnitude only. Displacement and velocity are vector quantities: they record magnitude and direction. Distance measures the total path length travelled, for example 5 km around a circuit, while displacement measures the straight-line distance from start to finish with a direction, for example 2 km east. Similarly, speed is how fast an object moves, while velocity is speed in a stated direction. A runner completing one lap of a 400 m track has travelled a distance of 400 m but has zero displacement, because the start and finish coincide. This distinction explains why average speed and average velocity can differ, and why direction must be given for vector quantities.
What earns the marks
- Classifies distance and speed as scalar quantities with magnitude only.
- Classifies displacement and velocity as vector quantities with magnitude and direction.
- Defines displacement as distance in a stated direction from the starting point.
- Explains that distance is the total path length travelled, regardless of direction.
- Uses an example such as a lap of a track to show distance is non-zero while displacement is zero.
- Explains that velocity is speed in a stated direction, whereas speed has no direction.
Common mistakes and how to put them right
Using distance and displacement as synonyms.
Put it right by stating that displacement includes direction and is measured from start to finish.
Assuming a moving object always has non-zero displacement.
Put it right by giving the example of returning to the starting point, where displacement is zero.
Giving speed when velocity is required.
Put it right by adding the direction of motion to the speed value.
Exam tips
- When comparing scalar and vector quantities, state clearly which quantity has direction and which does not.
- Use a labelled example, such as a there-and-back journey, to show the difference between distance and displacement.
- Check whether the question asks for speed or velocity, and include direction only for velocity.
Try the lesson
The start of the Velocity: Students should be able to explain the vector–scalar distinction as it applies to displacement, distance, velocity and speed. lesson, made from checked teaching notes for this specification point.
Have a go first
Which of these quantities is a scalar?
Listen
Distance and speed are scalar quantities: they record magnitude only. Displacement and velocity are vector quantities: they record magnitude and direction. Distance measures the total path length travelled, for example 5 km around a circuit, while displacement measures the straight-line distance from start to finish with a direction, for example 2 km east. Similarly, speed is how fast an object moves, while velocity is speed in a stated direction. A runner completing one lap of a 400 m track has travelled a distance of 400 m but has zero displacement, because the start and finish coincide. This distinction explains why average speed and average velocity can differ, and why direction must be given for vector quantities. A strong answer earns marks for these points. Classifies distance and speed as scalar quantities with magnitude only. Classifies displacement and velocity as vector quantities with magnitude and direction. Defines displacement as distance in a stated direction from the starting point. Explains that distance is the total path length travelled, regardless of direction. A common slip: Using distance and displacement as synonyms. Instead, stating that displacement includes direction and is measured from start to finish. Exam tip: When comparing scalar and vector quantities, state clearly which quantity has direction and which does not.
See it
Key words
Say what each word means before you turn the card.
Distance
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Displacement
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Speed
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Velocity
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See every definition
- Distance
- The total path length travelled, regardless of direction.
- Displacement
- The straight-line distance from start to finish, with a direction, measured from the starting point.
- Speed
- How fast an object moves, recording magnitude only with no direction.
- Velocity
- Speed in a stated direction, so it records magnitude and direction.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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