Quantities & Units in Mechanics — A-Level Mathematics Revision

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What is Quantities & Units in Mechanics?

Quantities and units in mechanics at A-Level focuses on the fundamental physical quantities used to describe motion and forces. You will learn about the SI system of units and how to use them consistently in calculations, as well as the distinction between scalar and vector quantities.

Board notes: All A-Level Maths boards (AQA, Edexcel, OCR) cover quantities and units in mechanics as a fundamental part of the applied mathematics content.

Worked example

Common mistakes

• 1Confusing mass and weight. Mass is a measure of the amount of matter in an object (measured in kg), while weight is the force of gravity acting on an object (measured in N).
• 2Using inconsistent units in calculations. All quantities should be converted to their base SI units (e.g., metres, kilograms, seconds) before being used in a formula.
• 3Not understanding the difference between scalar and vector quantities. A scalar has magnitude only (e.g., speed, distance), while a vector has both magnitude and direction (e.g., velocity, displacement).

Quantities & Units in Mechanics exam questions

Exam-style questions for Quantities & Units in Mechanics with mark-scheme style solutions and timing practice. Aligned to AQA, Edexcel and OCR specifications.

Frequently asked questions

• What are the base SI units?

  The base SI units are the metre (m) for length, the kilogram (kg) for mass, the second (s) for time, the ampere (A) for electric current, the kelvin (K) for temperature, the mole (mol) for amount of substance, and the candela (cd) for luminous intensity.

• What is a derived unit?

  A derived unit is a unit that is formed from a combination of the base SI units. For example, the unit of force, the newton (N), is a derived unit equivalent to kg m/s².