EJC Physics H201 Measurement 2023_1. Notes (FULL)

Page 1 of 23 9749(202 3) H2 Physics H201 Measurement – Notes H2 Topic 01 – Measurement Content • Physical quantities and SI units • Scalars and vectors • Errors and uncertainties Learning Outcomes Candidates should be able to: (a) recall the following base quantities and their SI units: mass (kg), length (m), time (s), current (A), temperature (K), amount of substance (mol) (b) express derived units as products or quotients of the base units and use the named units listed in ‘Summary of Key Quantities, Symbols and Units’ as appropriate (c) use SI base units to check the homogeneity of physical equations (d) show an understanding of and use the conventions for labelling graph axes and table columns as set out in the ASE publication Signs, Symbols and Systematics (The ASE Companion to 16-19 Science, 2000) (e) use the following prefixes and their symbols to indicate decimal sub- multiples or multiples of both base and derived units: pico (p), nano (n), micro (µ), milli (m), centi (c). deci (d), kilo (k), mega (M), giga (G), tera (T) (f) make reasonable estimates of physical quantities included within the syllabus (g) distinguish between scalar and vector quantities, and give examples of each (h) add and subtract coplanar vectors (i) represent a vector as two perpendicular components (j) show an understanding of the distinction between systematic errors (including zero error) and random errors (k) show an understanding of the distinction between precision and accuracy (l) assess the uncertainty in a derived quantity by addition of actual, fractional, percentage uncertainties or by numerical substitution (a rigorous statistical treatment is not required). * Additional requirement for 8867 H1 Physics (2020) subsumed under H208 Temperature and Ideal Gases (e) state that 1 mole of any substance contains 6.02 × 10 23 particles & use the Avogadro number NA = 6.02 × 1023 mol-1

Page 2 of 23 9749(202 3) H2 Physics H201 Measurement – Notes 1.0 Introduction: The Nature of Science Science is a durable body of knowledge de rived from empirical and repeatable observations. Despite this, science knowledge is also tentative: it is neither set in concrete nor perfect. Rather, it is subject to change. A scientific law describes an observed phenomenon while a scientific theory explains it. The tentative nature of science also means that laws and theories may be updated in the light of new evidence or new interpretation of existing evidence. Since science demands and relies on empirical evidence, a system of measurements is important to allow meaningful and objective comparisons between observations. 1.1 Physical Quantities and Units A physical quantity is a property of a material or system that can be quantified by measurement. Each quantity consists of a numerical magnitude and a unit. We adopt SI units. The SI was founded on 7 base quantities, by which all other physical quantities in the SI