Physical quantities, units and measurement
SI quantities, prefixes, scale, instrument choice, scalars and vectors.
Learning goals
- Represent a physical quantity with a numerical magnitude and unit
- Recall the six prescribed SI base quantities and their units
- Use the prescribed SI prefixes from nano to tera
- Compare orders of magnitude from a typical atom to the Earth
- Select and justify measuring instruments by range and precision
- Distinguish scalar and vector quantities and give examples
G3 Science (Physics) · Topic 1
Begin with the complete topic lesson. Then try a short check, use the feedback to review one idea and come back later for another attempt.
Build the idea in order
- Quantities and units
- Scale and prefixes
- Suitable instruments
- Scalars and vectors
Lessons
Physical quantities, units and measurement
Represent physical quantities precisely, convert SI prefixes, select instruments, and classify scalar and vector quantities.
Check your understanding
Physical quantities, units and measurement topic check
Check the required topic capabilities and get focused practice for ideas that need another look.
G3 Science Structured Practice — Measurement, Force and Pressure
Marked practice for G3 Science measurement and pressure: unit and area conversions, reading scales, choosing instruments, density and contact pressure.
What to remember
- Write a physical quantity as a numerical magnitude with a unit.
- Recall the six required base units and convert prefixes by applying the factor to the whole unit.
- Estimate the scale of an object before choosing an instrument with suitable range and precision.
- Use repeated readings, derived measurements and careful scale reading when one direct reading is unreliable.
- A vector has direction as well as magnitude and unit; a scalar does not.
Topic and syllabus information
Physical quantities, units and measurement is Topic 1 in K326 / K327 Physics component · 2027.
The lesson and questions stay at the depth required for this course.
Reviewed 9 Aug 2026
Continue with the next resource in this course.
Course and syllabus information
- Course
- SEC G3 Combined Science Physics component
- Edition
- SEC G3 Combined Science Physics component 2027