Measurement JPJC Notes

1 JURONG PIONEER JUNIOR COLLEGE 9749 H2 PHYSICS /8867 H1 PHYSICS 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 nam ed 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 pub lication 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 ( ), 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 errors) 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).

2 Introduction ▪ Physics aims to understand the natural world around us and to represent the various phenomenon via mathematical relationships. Scientific experiments are then designed to test out the validity of the mathematical relationships. ▪ Such experiments involve the measurements of various physical quantities. The reliability of the measurements is important so as to correctly verify the concepts and theories. The precisions of any experimental results should also be quoted to an appropriate numbers of significant figures to reflect on the order or accuracy. ▪ In this lecture, we will learn to use different physical quantities , their SI units and how to work with the errors and uncertainties incurred when taking measurements. We will also be learning the classification of physical qu antities as scalars or vectors, the addition and subtraction of vectors and the resolving of a vector into its components. 1 SI units (a) Candidates should be able to recall the following base quantities and their units: mass (kg), length (m), time (s) , current (A), temperature (K), amount of substance (mol). 1.1 Physical quantities  Physical quantities are quantities t