Chapter 1: Measurement

1.1 Physical Quantities

• Measurement is a method to determine the value of a physical quantity. (p.4)
• Physical quantities consist of base quantities and derived quantities. (p.4)
• Base quantities: length, mass, time, electric current, thermodynamic temperature, luminous intensity, amount of substance. (p.4)

Base Quantities and S.I. Units

(p.6)

Base quantity	Symbol	S.I. unit	Symbol
Length	l	metre	m
Mass	m	kilogram	kg
Time	t	second	s
Thermodynamic temperature	T	kelvin	K
Electric current	I	ampere	A
Luminous intensity	Iv	candela	cd
Amount of substance	n	mole	mol

Derived Quantities

• Volume, V = l³ (p.7)
• Density, ρ = m / V (p.7)
• Velocity, v = l / t (p.7)
• Charge, Q = I × t (p.7)
• Force, F = m × a → unit: newton (N) (p.7)
• Pressure, P = F / A → unit: pascal (Pa) (p.7)
• Energy / Work, W = F × l → unit: joule (J) (p.7)

Scalar and Vector Quantities

• Scalar quantity has magnitude only. (p.8)
• Vector quantity has both magnitude and direction. (p.8)
• Scalar examples: distance, area, length, work, temperature, density. (p.9)
• Vector examples: displacement, velocity, force, acceleration, momentum. (p.9)

1.2 Scientific Investigation — Interpreting Graphs

• Straight line with positive gradient through the origin: y ∝ x; gradient m = Δy/Δx; y = mx. (p.10)
• Straight line with positive or negative gradient, not through the origin: y = mx + c. (p.10)
• Curve, or straight line of y against 1/x through the origin: y ∝ 1/x (inverse relationship). (p.11)
• Five aspects of analysing graphs: the relationship between two variables, gradient of the graph, area under the graph, interpolation, and extrapolation. (p.12)