DHS 01 Measurements (Lecture Notes & Tutorial)

Dunman High School (Senior High Physics) 1 Topic 1 - Measurement Guiding Questions  How are the standards for measurements established?  Why is uncertainty inherent in all measurements?  How can uncertainties be estimated? How can they be reduced if necessary?  Why does the uncertainty of a measurement matter?  How is the skill of making estimate s of physical quantities useful and how can this skill be developed? Contents  Physical quantities & SI Units  Scalars and vectors  Errors and uncertainties Learning Outcomes Students should be able to: (a) recall the following base quantities and their units : mass (kg), length (m), time (s), current (A), temperature (K), amount of substance (mol). (b) express derived units as products or quotient s 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 physi cal 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 s ystematic errors (including zero errors) and random errors. (k) show an understanding of the dist inction between precision and accuracy. (l) assess the uncertainty in a derived quantity by addi tion of actual, fractional or percentage uncertainties or numerical substitution (a rigorous statistical treatment is not required). 1 Physical Quantities and SI Units Any scientifically measurable quantities are called physical quantities. e.g. temperature, force, current, pressure, mass, energy, etc. All physical quantities consist of a numerical value and a unit. e.g. mass, m = 65.0 kg The Summary of some Quantities and Units used in the A-Level examination is given in Appendix 1. Physical Quantity Numerical value unit

Dunman High School Year 5 Physics 2024/2025 2 In very much the same way that languages have deve loped in various parts of the world, different units of measurements have evolved. Just as languages can be translated from one to another, units of measurement can be converted between systems. For standardisation, it is much better to have just one system of units. Scientists use the Système International (SI) which is based on the metric system. LO(a) recall the following b