Physical Quantities & SI Units — A/L Physics

What must I remember about Physical Quantities & SI Units?

• Base Physical Quantities & SI Units: Length (m), Mass (kg), Time (s), Electric Current (A), Thermodynamic Temperature (K), Amount of Substance (mol), Luminous Intensity (cd).
• Supplementary SI Units: Plane angle measured in radians (rad); Solid angle measured in steradians (sr).
• Derived Quantities: Quantities algebraically expressed in terms of base quantities (e.g., Force in N = kg·m·s⁻², Energy in J = kg·m²·s⁻², Pressure in Pa = kg·m⁻¹·s⁻²).
• SI Prefixes and Engineering Formats: Standard decimal multipliers ranging from pico (10⁻¹²), nano (10⁻⁹), micro (10⁻⁶), milli (10⁻³) up to kilo (10³), mega (10⁶), giga (10⁹), tera (10¹²).

Test yourself (1 minute)

1. Unit formatting rules

   Never use plural forms for unit symbols (write 10 kg, not 10 kgs); use a small space between numeric value and unit (5 m, not 5m).

2. Celsius to Kelvin conversion

   T(K) = θ(°C) + 273.15; note that temperature interval 1 K is identically equal to 1 °C (ΔT = Δθ).

3. Proper derived unit expansion

   Always reduce derived units to SI base units when checking equivalence (e.g., 1 Pa = 1 N/m² = 1 kg·m⁻¹·s⁻²).

Practise Physical Quantities & SI Units questions today

Source: NIE G.C.E. (A/L) Physics Resource Book - Unit 1: Measurement

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Where does Physical Quantities & SI Units fit in the syllabus?

Unit 1.2 · Year 1 · Term 1