01 Measurement (H2) 2020 - Student

1-1 ST. ANDREW’S JUNIOR COLLEGE JC 1 PHYSICS 2020 TOPIC 1: MEASUREMENT 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 indicat e deci mal 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 zer o 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). 1. SI Units (Le Système International d’Unités) A quantity is s omething that can be measured. Time is an example of a quantity. When physicists quote time intervals, they would use a numerical magnitude and a unit. An example of a measured time interval would be 9.58 seconds where “9. 58” represents a number (numerical magnitude) and “seconds” represents a unit in which time can be measured in. For a quantity to be meaningful, the unit is as important as the numerical magnitude: 9 seconds is certainly different from 9 hours. 1.1 Base Quantities and their Units The SI system of units consists of 7 base units in which all other units can be derived from using suitable combination of these base units. Base Quantities SI Base Units Name Symbol Length metre m Mass kilogram kg Time second s Amount of substance mole mol Temperature kelvin K Current ampere A *Luminous intensity candela cd Note: *Luminous intensity is not required in the syllabus.

1-2 1.2 Derived Quantities and their Units A derived quantity is linked to other quantities via a valid equation. Examples of derived quantities (with their units) Derived Quantities Equation Derived Units Area (A) A = l2 m2 Volume (V) V = l3 m3 Density ()  = m / V kg / m3 = kg m-3 Velocity (v) v = l / t m / s = m s-1 Acceleration (a) a = v / t (m s-1) / s = m s-2