A physics student is comparing four physical quantities: displacement, speed, acceleration, and energy. For each quantity, state whether it is a scalar quantity or a vector quantity, and give the correct SI unit.

Pearson Edexcel International GCSE Physics (4PH1) — 1.1 Units · State · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A student revising for an examination writes that all four quantities — displacement, speed, acceleration, and energy — have the same type of unit, measured in SI base units only. The student also claims that all four are vector quantities.

Model answer (4 marks)

Displacement: vector, m
Speed: scalar, m/s
Acceleration: vector, m/s²
Energy: scalar, J

Examiner tips

Use the word ‘vector’ or ‘scalar’ first, then the unit; keep the unit in correct SI form.
Write the units exactly as shown: m, m/s, m/s², J.
Check that you don’t mix up speed (scalar) with velocity (vector).

Common mistakes

Writing speed as a vector or using m/s² for speed.
Using the wrong unit for energy, e.g. J/m or J/s.
Confusing displacement with distance or velocity.

Mark scheme (4 marks)

Displacement is a vector quantity with the unit metres (m).
Speed is a scalar quantity with the unit metres per second (m/s).
Acceleration is a vector quantity with the unit metres per second squared (m/s²).
Energy is a scalar quantity with the unit joules (J).

Key terms in this question

scalar quantity · vector quantity · displacement · acceleration