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EnglandPhysics

3.1 Measurements and their errors

3 dot points across 3 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How can orders of magnitude and sensible estimates let a physicist sanity-check an answer without precise data?

Orders of magnitude, estimation of approximate values of physical quantities to the nearest power of ten, and using such estimates to check the plausibility of calculated results.
A focused answer to AQA A-Level Physics 3.1.3, covering orders of magnitude, estimating physical quantities to the nearest power of ten, and using these estimates to check whether a calculated result is plausible.
8 min answer →

Why does every measurement carry an uncertainty, and how do we quantify and combine those uncertainties?

Random and systematic errors, precision and accuracy, repeatability and reproducibility, absolute, fractional and percentage uncertainty, and how uncertainties combine and are shown on graphs.
A focused answer to AQA A-Level Physics 3.1.2, covering random and systematic errors, the difference between precision and accuracy, how to express absolute, fractional and percentage uncertainties, how to combine them, and how uncertainty appears on graphs as error bars.
10 min answer →

How do SI base units, derived units and prefixes give every physical quantity a consistent description?

SI base units, units derived from them, the use of standard prefixes, and checking equations for homogeneity using base units.
A focused answer to AQA A-Level Physics 3.1.1, covering the SI base units, how derived units are built from them, the standard prefixes from pico to tera, and how to test an equation for homogeneity using base units.
9 min answer →