WJEC A-Level Physics Unit 1 Motion, Energy and Matter: a complete overview of kinematics, dynamics, energy, materials, stars and nuclear structure

What Unit 1 actually demands

Unit 1 Motion, Energy and Matter is the foundation of the whole WJEC course. It sets up the language of physics (units, vectors and equilibrium), then builds the mechanics that everything else relies on: kinematics, dynamics and energy. It finishes with three application-rich topics, solids under stress, using radiation to investigate stars and particles and nuclear structure, which reward precise definitions as much as calculation.

This guide walks through the seven topics of the unit in specification order, then sets out the exam patterns WJEC repeats. Each topic has a matching dot-point page with practice questions; this overview ties them together.

Basic physics

The unit opens with the toolkit: SI base units and prefixes, homogeneity of equations (checking units balance), the difference between scalars and vectors, resolving and adding vectors, density $\rho = m/V$, and the equilibrium of coplanar forces including the principle of moments. WJEC expects you to resolve forces into perpendicular components and to take moments about a sensible point.

Kinematics

Kinematics describes motion without asking what causes it. You define displacement, velocity and acceleration, interpret motion graphs (gradient of a displacement-time graph is velocity, area under a velocity-time graph is displacement), and apply the equations of motion for constant acceleration, $v = u + at$, $x = ut + \frac{1}{2}at^2$ and $v^2 = u^2 + 2ax$. Projectile problems treat horizontal and vertical motion independently.

Dynamics

Dynamics introduces Newton's three laws, the link between force and rate of change of momentum ($F = \frac{\Delta p}{\Delta t}$), and the principle of conservation of momentum in collisions. WJEC distinguishes elastic collisions (kinetic energy conserved) from inelastic ones (kinetic energy not conserved), and asks you to identify Newton's-third-law force pairs precisely.

Energy concepts

This topic defines work as $W = Fx\cos\theta$, kinetic energy $E_k = \frac{1}{2}mv^2$, gravitational potential energy $E_p = mgh$, the principle of conservation of energy, power $P = \frac{W}{t} = Fv$, and efficiency as useful output over total input. Energy questions often combine with kinematics and dynamics in a single structured problem.

Solids under stress

Materials physics covers Hooke's law $F = k\Delta x$, stress $\sigma = F/A$, strain $\varepsilon = \Delta L/L$ and the Young modulus $E = \sigma/\varepsilon$. You interpret stress-strain graphs (elastic limit, yield, ultimate tensile stress), distinguish elastic from plastic behaviour, and calculate the elastic strain energy as the area under a force-extension graph. Measuring the Young modulus of a wire is a specified practical.

Using radiation to investigate stars

This astrophysics topic treats a star as a black body. You use Wien's displacement law $\lambda_{max} T = 2.90 \times 10^{-3}\,\text{m K}$ to find surface temperature from the peak wavelength, Stefan's law $P = \sigma A T^4$ to link luminosity to temperature and radius, and the inverse-square law of intensity to relate luminosity and observed intensity. Stellar spectra and the hydrogen absorption lines also feature.

Particles and nuclear structure

The unit closes with the standard model as WJEC frames it: quarks (up and down) and leptons (electron and electron-neutrino), their antiparticles, and the classification of hadrons into baryons (three quarks) and mesons (a quark and an antiquark). You apply conservation laws (charge, baryon number, lepton number) to test whether a reaction is allowed, and describe beta-minus and beta-plus decay at the quark level.

How Unit 1 is examined

WJEC Unit 1 is an AS written paper of about 1 hour 30 minutes carrying 80 marks. Questions are structured and written directly from the specification statements, so revise statement by statement. Around 40 per cent of marks are mathematical, so rearranging equations, vector resolution and graph work must be automatic. The specified practical on the Young modulus, and the standard derivations and definitions in dynamics and energy, recur every series.

The seven topics, dot point by dot point

Each topic has a dot-point answer page with worked exam questions and cross-links. Browse them from this unit overview and the subject hub.

For the official specification

WJEC publishes the full specification, past papers and mark schemes at wjec.co.uk. Always revise from the current specification and WJEC's own past papers, because question style is board-specific.