What does VCE Physics Unit 3 cover?

Unit 3 (How do fields explain motion and electricity?) covers Newtonian motion in two dimensions (projectiles, circular motion, momentum), gravitational fields, electric fields, magnetic fields, and electromagnetic induction including generators and transformers.

What does VCE Physics Unit 4 cover?

Unit 4 (How have new ideas and ways of thinking developed our understanding of the physical world?) covers wave behaviour of light (interference, polarisation, refraction), photon model of light (photoelectric effect, atomic spectra), matter waves and de Broglie, and wave-particle duality.

How are exam problems structured?

Short-answer questions worth 2-5 marks each, plus extended-response items worth 6-10 marks. Multiple choice in Section A. Section B requires multi-step working: identify the physics, write the formula, substitute values, calculate, state units.

What are the most-tested calculation types?

Projectile motion (horizontal range, maximum height), uniform circular motion ($F = mv^2/r$), gravitational orbits (Kepler's third law), electromagnetic induction (Faraday's law, transformer turns ratio), wave-related ($v = f\lambda$, photon energy $E = hf$, de Broglie $\lambda = h/p$).

How should multi-mark working be presented?

Always show: the physics principle being applied; the formula in symbolic form; substitution with units; calculation; final answer with units and appropriate significant figures (typically 3 sig fig).

What are the most common student errors?

Forgetting to convert units (mm to m, kJ to J). Wrong sign convention (vector quantities). Forgetting to include gravitational acceleration in projectile problems. Sign errors in conservation equations. Using the wrong form of $P = VI = I^2 R = V^2/R$ for available knowns.

VICPhysics

VCE Physics worked exam problems by Area of Study: the 2026 guide

A complete guide to VCE Physics Unit 3-4 worked exam problems. Sample questions and step-by-step solutions for each Area of Study, organised by typical problem type.

Generated by Claude Opus 4.816 min readVCAA-PHY-WORKEDUpdated 2026-06-21

Reviewed by: AI editorial process; not yet individually human-reviewed

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What this guide is for
Unit 3 AoS 1: Motion in two dimensions
Unit 3 AoS 2: Fields and forces
Unit 3 AoS 3: Electromagnetic induction
Unit 4 AoS 1: Light and matter
Unit 4 AoS 2 (interference and waves)
Multi-mark working pattern
Check your knowledge

What this guide is for

VCE Physics Unit 3-4 exam preparation requires fluency with calculation patterns across all areas of study. This guide presents worked problems for each AoS, with step-by-step solutions showing the marking conventions VCAA expects.

Unit 3 AoS 1: Motion in two dimensions

Projectile motion

Problem. A ball is thrown horizontally at 15 m/s from a height of 20 m. (a) Time to hit the ground. (b) Horizontal range.

Solution.

(a) Vertical motion: $s = ut + \frac{1}{2}at^2$ . $u = 0$ vertical, $a = 9.8$ m/s $^2$ down, $s = 20$ m.

$20 = 0 + \frac{1}{2}(9.8)t^2$
$t^2 = 40/9.8 = 4.08$
$t = 2.02$ s.

(b) Horizontal motion: $x = v_x t = 15 \times 2.02 = 30.3$ m.

Figure 1. Horizontal-launch projectile: panel (a) shows the true parabolic trajectory (41 computed samples) from a 20-metre cliff with three time snapshots; panel (b) is the velocity-decomposition inset at t = 1.0 s where vx stays at 15 m/s and vy = gt = 9.8 m/s.

Circular motion

Problem. A car of mass 1200 kg goes around a curve of radius 50 m at 20 m/s. Find the centripetal force.

Solution. $F_c = mv^2/r = 1200 \times 400 / 50 = 9600$ N.

Figure 2. Two-snapshot view of uniform circular motion: v is always tangent (anticlockwise) and Fc always radially inward. The side inset gives the symbolic formula and the numerical substitution.

Unit 3 AoS 2: Fields and forces

Gravitational

Problem. A satellite orbits Earth in a circular orbit of radius $r = 7.0 \times 10^6$ m. Find its orbital period. ( $GM = 3.99 \times 10^{14}$ m $^3$ /s $^2$ .)

Solution. $T^2 = \frac{4\pi^2 r^3}{GM} = \frac{4\pi^2 (7 \times 10^6)^3}{3.99 \times 10^{14}}$ .

$r^3 = 3.43 \times 10^{20}$ . $T^2 = 4\pi^2 \times 3.43 \times 10^{20} / 3.99 \times 10^{14} = 3.39 \times 10^7$ . $T = 5821$ s $\approx 97$ min.

Electric field between parallel plates

Problem. A 12 V battery is connected across parallel plates 2.0 mm apart. (a) Field strength? (b) Force on an electron in the field?

Solution.

(a) $E = V/d = 12 / 0.002 = 6000$ V/m.

(b) $F = qE = 1.6 \times 10^{-19} \times 6000 = 9.6 \times 10^{-16}$ N.

Unit 3 AoS 3: Electromagnetic induction

Faraday's law

Problem. A coil of 200 turns with area 0.040 m $^2$ is in a magnetic field that changes from 0.20 T to 0.50 T in 0.50 s. Find the induced EMF.

Solution. $\Delta \Phi$ per turn = $\Delta B \times A = 0.30 \times 0.040 = 0.012$ Wb.

$\varepsilon = N \frac{\Delta \Phi}{\Delta t} = 200 \times 0.012 / 0.50 = 4.8$ V.

Figure 3. Faraday and Lenz at work: an increasing external field into the page induces an anticlockwise current in the loop (so the coil's own field opposes the increase), and the side inset gives the symbolic and numerical induced EMF for the worked example.

Transformer

Problem. A transformer has 500 primary turns and 100 secondary turns. Input 240 V at 0.5 A. Find secondary voltage and current (ideal transformer).

Solution. $V_s / V_p = N_s / N_p = 100/500 = 1/5$ . $V_s = 48$ V.

Power conservation: $V_p I_p = V_s I_s$ . $I_s = V_p I_p / V_s = 240 \times 0.5 / 48 = 2.5$ A.

Unit 4 AoS 1: Light and matter

Photoelectric effect

Problem. Light of frequency $7.5 \times 10^{14}$ Hz incident on a metal with work function 2.4 eV. ( $h = 4.14 \times 10^{-15}$ eV s.) Find $E_{k,max}$ of ejected electrons.

Solution. Photon energy $= hf = 4.14 \times 10^{-15} \times 7.5 \times 10^{14} = 3.1$ eV.

$E_{k,max} = hf - \phi = 3.1 - 2.4 = 0.7$ eV.

de Broglie

Problem. An electron is accelerated through 200 V. Find its de Broglie wavelength.

Solution. Shortcut: $\lambda = 1.226 / \sqrt{V}$ nm $= 1.226/\sqrt{200} = 0.087$ nm.

Unit 4 AoS 2 (interference and waves)

Young's double-slit

Problem. Light $\lambda = 600$ nm, slits 0.20 mm apart, screen 1.5 m away. Find fringe spacing.

Solution. $\Delta x = \lambda L / d = 600 \times 10^{-9} \times 1.5 / 0.20 \times 10^{-3} = 4.5 \times 10^{-3}$ m $= 4.5$ mm.

Malus's law

Problem. Unpolarised light intensity $I_0$ passes through a polariser, then through a second at 30 degrees to the first. Find the final intensity.

Solution. After first polariser: $I_0/2$ . After second (Malus): $(I_0/2) \cos^2(30) = (I_0/2)(3/4) = 3 I_0/8$ .

Multi-mark working pattern

For each numerical question:

State the principle (Faraday's law, Newton's second law).
Write the formula in symbolic form.
Substitute values with units.
Calculate with appropriate significant figures.
State the answer with units.

VCAA awards method marks for correct identification of the principle and formula, even if the calculation slips.

Check your knowledge

A broad VCAA-style mix across the four Areas of Study, set as it would appear on the November paper. Attempt under exam conditions before checking the solutions block.

State the difference between displacement and distance for an object in 2-D motion, and give an example where they differ by a factor of two. (2 marks)
A projectile is launched at 25 m s $^{-1}$ at 50 degrees above horizontal from ground level on a still day. Taking $g = 9.80 \ \text{m s}^{-2}$ , calculate (a) the time of flight, (b) the maximum height, (c) the range. (5 marks)
(a, 3) A satellite is placed in low Earth orbit (LEO) at altitude 350 km. Calculate the orbital speed and period. ( $G = 6.67 \times 10^{-11} \ \text{N m}^{2} \text{kg}^{-2}$ , $M_E = 5.98 \times 10^{24} \ \text{kg}$ , $R_E = 6.37 \times 10^{6} \ \text{m}$ .) (b, 2) State why LEO satellites must be re-boosted periodically and what eventually happens if they are not. (5 marks)
A current of 8.0 A flows in a 25-turn rectangular coil of dimensions 0.080 m by 0.050 m. The coil is in a 0.30 T uniform magnetic field, with its plane parallel to the field. (a) Calculate the torque on the coil. (b) State the angle at which torque is zero and explain why the coil is unstable at that orientation in an undriven motor. (5 marks)
(a, 3) An electron in a hydrogen atom drops from $n = 4$ to $n = 1$ . Using $E_n = -13.6 / n^2 \ \text{eV}$ , calculate the photon energy and wavelength. (b, 2) State and identify the spectral region (UV, visible, IR) of the emitted photon. (5 marks)
A spaceship travels from Earth to Alpha Centauri (4.0 light-years in Earth's frame) at $v = 0.60c$ . (a) Calculate the Lorentz factor. (b) Calculate the Earth-frame travel time. (c) Calculate the proper time experienced by the crew. (d) Calculate the Alpha Centauri distance measured in the spaceship's frame. (7 marks)
(a, 3) Two parallel plates separated by 5.0 mm are connected to a 2000 V supply. Calculate the electric field between the plates and the force on an electron between them. (b, 3) The electron, initially at rest at the negative plate, traverses the gap. Calculate its kinetic energy on reaching the positive plate, and its speed (treat non-relativistically; $m_e = 9.11 \times 10^{-31} \ \text{kg}$ ). (6 marks)
A practical-investigation data set tests Hooke's law for a steel spring. Force (N) versus extension (m): (1.0, 0.0205), (2.0, 0.0398), (3.0, 0.0612), (4.0, 0.0808), (5.0, 0.1005). (a) State Hooke's law and the expected graph. (b) Calculate the spring constant from the first and last points and comment on whether the data are consistent with Hooke's law across the full range. (c) Estimate the uncertainty in the spring constant if each extension is read to $\pm 0.5 \ \text{mm}$ and each force to $\pm 0.05 \ \text{N}$ . (6 marks)

Solutions

Q1: Displacement is the straight-line vector from start to finish position; distance is the total scalar path length covered. Example: a runner who jogs 200 m around a semicircular track returns 127 m closer to start as a straight line ( $\Delta r = 2 \times R = 2 \times 200/\pi = 127$ m), so displacement is 127 m while distance is 200 m, almost exactly a factor of two apart.
Q2: $u_x = 25 \cos 50^\circ = 16.07 \ \text{m s}^{-1}$ ; $u_y = 25 \sin 50^\circ = 19.15 \ \text{m s}^{-1}$ . (a) Time of flight $= 2 u_y / g = 2 \times 19.15 / 9.80 = 3.91 \ \text{s}$ . (b) Max height $= u_y^2 / 2g = (19.15)^2 / 19.6 = 18.7 \ \text{m}$ . (c) Range $= u_x \times T = 16.07 \times 3.91 = 62.8 \ \text{m}$ .
Q3: (a) $r = 6.37 \times 10^{6} + 3.50 \times 10^{5} = 6.72 \times 10^{6} \ \text{m}$ . $v = \sqrt{GM/r} = \sqrt{6.67 \times 10^{-11} \times 5.98 \times 10^{24} / 6.72 \times 10^{6}} = \sqrt{5.94 \times 10^{7}} = 7.71 \times 10^{3} \ \text{m s}^{-1}$ . $T = 2\pi r/v = 2\pi \times 6.72 \times 10^{6}/7.71 \times 10^{3} = 5.48 \times 10^{3} \ \text{s} = 91.3 \ \text{minutes}$ . (b) Atmospheric drag at 350 km is non-negligible; without periodic re-boost, the satellite spirals inward, loses altitude, heats catastrophically and burns up on re-entry within a few years.
Q4: (a) For a coil with its plane parallel to the field, the moment arm is at maximum. Torque $\tau = N B I A = 25 \times 0.30 \times 8.0 \times (0.080 \times 0.050) = 25 \times 0.30 \times 8.0 \times 4.0 \times 10^{-3} = 0.24 \ \text{N m}$ . (b) Torque is zero when the coil's plane is perpendicular to the field (the field threads the coil along the normal). In an undriven motor (no commutator current reversal) the coil overshoots this position and reverses direction, settling at the zero-torque orientation; the equilibrium is stable if the field still threads in the same direction, but a small perturbation drives the coil back. In a motor with a commutator, this is the "dead point" where current must reverse to maintain rotation.
Q5: (a) $E_4 - E_1 = -13.6/16 - (-13.6/1) = -0.85 + 13.6 = 12.75 \ \text{eV}$ . $\lambda = hc/E = 1240/12.75 = 97.3 \ \text{nm}$ . (b) 97 nm lies in the deep ultraviolet (the Lyman series), invisible to the human eye and absorbed strongly by atmospheric oxygen.
Q6: (a) $\gamma = 1/\sqrt{1 - 0.36} = 1/\sqrt{0.64} = 1/0.80 = 1.25$ . (b) Earth-frame time $= 4.0 \ \text{ly} / 0.60c = 4.0/0.60 = 6.67 \ \text{years}$ . (c) Proper time $\tau_0 = t/\gamma = 6.67/1.25 = 5.33 \ \text{years}$ . (d) Contracted distance $L = L_0/\gamma = 4.0/1.25 = 3.20 \ \text{ly}$ . Crew traverse 3.20 ly at $0.60c$ in their frame, taking $3.20/0.60 = 5.33 \ \text{years}$ , matching part (c).
Q7: (a) $E = V/d = 2000/0.005 = 4.00 \times 10^{5} \ \text{V m}^{-1}$ . Force $F = eE = 1.60 \times 10^{-19} \times 4.00 \times 10^{5} = 6.40 \times 10^{-14} \ \text{N}$ . (b) $KE = eV = 1.60 \times 10^{-19} \times 2000 = 3.20 \times 10^{-16} \ \text{J}$ . $v = \sqrt{2KE/m_e} = \sqrt{2 \times 3.20 \times 10^{-16}/9.11 \times 10^{-31}} = \sqrt{7.03 \times 10^{14}} = 2.65 \times 10^{7} \ \text{m s}^{-1}$ . This is roughly $0.09c$ , so non-relativistic treatment is acceptable (relativistic correction less than 0.5 percent).
Q8: (a) Hooke's law: $F = kx$ for a spring within its elastic limit; a graph of $F$ versus $x$ is a straight line through the origin with gradient equal to the spring constant $k$ . (b) Gradient $= (5.0 - 1.0)/(0.1005 - 0.0205) = 4.00/0.0800 = 50.0 \ \text{N m}^{-1}$ . Checking the intermediate points: at $F = 3.0$ , predicted $x = 0.0600$ , measured 0.0612 (within 2 percent); the data are consistent with Hooke's law across the entire range tested. (c) Relative uncertainty in extension over a typical reading $\Delta x / x = 0.0005/0.05 = 1.0$ percent. Relative uncertainty in force $\Delta F / F = 0.05/3.0 = 1.7$ percent. Combined (quadrature) for $k = F/x$ : $\sqrt{1.0^2 + 1.7^2} = 2.0$ percent. Absolute $\Delta k = 0.02 \times 50.0 = 1.0 \ \text{N m}^{-1}$ . So $k = (50.0 \pm 1.0) \ \text{N m}^{-1}$ .