Topic 1 establishes the measurement foundations used throughout IB Physics. Students learn to handle SI units, propagate uncertainties through calculations, and distinguish between vector and scalar quantities.
Seven SI base units: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), candela (cd). Derived units expressed as combinations (e.g., N = kg·m·s⁻², J = kg·m²·s⁻²). Metric prefixes from pico (10⁻¹²) to tera (10¹²). Orders of magnitude estimation for physical quantities.
Random errors: reduce by repeating measurements. Systematic errors: shift all measurements by a fixed amount (cannot be reduced by repetition). Absolute uncertainty: Δx. Fractional uncertainty: Δx/x. Percentage uncertainty: (Δx/x) × 100%. For addition/subtraction: add absolute uncertainties. For multiplication/division: add percentage uncertainties. For powers: multiply percentage uncertainty by the power.
Scalars have magnitude only (speed, mass, temperature, energy). Vectors have magnitude and direction (velocity, force, acceleration, momentum). Vector addition: tip-to-tail or parallelogram. Resolution into components: Fx = F·cosθ, Fy = F·sinθ. Resultant: R = √(Rx² + Ry²), direction θ = arctan(Ry/Rx).
Uncertainties appear in Paper 1 (MCQ) conceptual questions, Paper 2 data analysis, and especially in the Internal Assessment (IA). In the IA, you must collect raw data with uncertainties, propagate them through calculations, plot error bars on graphs, and evaluate whether results are consistent with accepted values. Strong uncertainty handling can earn maximum marks in the IA analysis criterion.
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