Physics: motion, forces, energy, circuits and waves
What this domain tests
NCEA Level 1 Physics asks you to describe motion, explain forces and energy transfers, apply simple circuit rules, and use the wave equation - often in unfamiliar contexts rather than textbook ones.
Core rules
- Speed vs velocity: speed = distance ÷ time (scalar); velocity is speed with direction. Acceleration = change in velocity ÷ time, so a car going round a corner at steady speed is still accelerating.
- Forces: weight W = mg (g ≈ 10 N kg⁻¹ on Earth) acts downward. Mass in kg does not change with location; weight does.
- Energy: energy is conserved, but transfers are never fully useful. Efficiency = useful output ÷ total input.
- Circuits: V = IR. In series, current is the same everywhere and voltages add; in parallel, voltage is the same across branches and currents add.
- Waves: v = fλ. Frequency is set by the source and stays the same when a wave crosses into a new medium; speed and wavelength change.
Worked example
A 1200 kg car accelerates from 5 m s⁻¹ to 25 m s⁻¹ in 8.0 s. a = (25 − 5) ÷ 8.0 = 2.5 m s⁻². Net force F = ma = 1200 × 2.5 = 3000 N. Kinetic energy gained = ½m(v² − u²) = ½ × 1200 × (625 − 25) = 360 000 J. Check with work done: average speed = 15 m s⁻¹, so d = 15 × 8 = 120 m; F × d = 3000 × 120 = 360 000 J. The two methods agree, which is what a marker looks for.
Traps that cost marks
- Giving weight in kg, or using g = 9.8 when the paper states 10.
- Treating velocity as a scalar in a direction-change question.
- Adding parallel resistors by simple addition (they combine as reciprocals).
- Substituting cm, g or mA without converting to SI first.
- Rounding mid-calculation, or dropping the unit from the final answer.