Understanding the Edexcel Physics Papers

The Edexcel A-Level Physics qualification (9PH0) is assessed through three written examination papers. Each paper tests different content areas, carries a different weighting, and demands a different approach. Before you start revising content, you need to understand the structure of the assessment you are preparing for — because structure shapes strategy.

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Paper 1: Advanced Physics I

• Duration: 1 hour 45 minutes
• Marks: 90
• Weighting: 30% of the total A-Level

Paper 1 covers the topics from the first half of the course: mechanics, electric circuits, materials, and waves. These are the foundational topics of physics, and many students feel most comfortable with them because they were studied first. However, familiarity can breed complacency — students often underperform on Paper 1 because they assume the topics are straightforward and do not revise them as carefully as later material.

The paper includes a mixture of multiple-choice questions, short-answer questions, calculations, and extended-response questions. Expect mechanics problems involving SUVAT equations, Newton's laws, and energy conservation. Circuit questions will test your understanding of Kirchhoff's laws, potential dividers, and internal resistance. Materials questions cover stress, strain, and Young's modulus. Waves questions span interference, diffraction, standing waves, and the electromagnetic spectrum.

Paper 1 Strategy

Start with the multiple-choice section and work through it methodically. For calculation questions, always write the equation you are using, substitute values with units, and present your final answer to an appropriate number of significant figures. For extended-response questions, plan your answer before writing.

graph TD
    A["Start Paper 1"] --> B["Multiple Choice Section"]
    B --> C["Read stem carefully"]
    C --> D["Eliminate obviously wrong options"]
    D --> E["Check remaining options against physics"]
    E --> F["Short Answer & Calculations"]
    F --> G["Write equation in symbols"]
    G --> H["Substitute values WITH units"]
    H --> I["Show rearrangement if needed"]
    I --> J["Answer + units + sig figs"]
    J --> K["Extended Response 6-mark"]
    K --> L["Plan for 60 seconds"]
    L --> M["Write structured answer with terminology"]
    M --> N["Final 10 min: check units, sig figs, blanks"]

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Paper 2: Advanced Physics II

• Duration: 1 hour 45 minutes
• Marks: 90
• Weighting: 30% of the total A-Level

Paper 2 covers the second half of the specification: further mechanics (momentum, circular motion), electric and magnetic fields, nuclear and particle physics, and thermodynamics. These topics tend to be more abstract and mathematically demanding. Many students find fields and nuclear physics particularly challenging.

Expect questions on gravitational and electric field calculations, capacitor charge and discharge, electromagnetic induction, nuclear decay equations, and the standard model of particle physics. Thermodynamics questions will test your understanding of the ideal gas laws, internal energy, and specific heat capacity.

Paper 2 Strategy

Paper 2 rewards students who are comfortable with multi-step calculations. Practise rearranging equations with several variables and working through problems that combine two or more concepts (for example, circular motion combined with gravitational fields for satellite orbits). Field questions often require you to choose between equations for uniform and radial fields — be sure you know when each applies.

Paper 2 Topic Difficulty Map

Topic	Common Pitfall	Exam Tip
Further mechanics	Forgetting momentum is a vector	Always state your positive direction
Gravitational fields	Mixing up g = GM/r² and V = -GM/r	Field strength uses 1/r², potential uses 1/r
Electric fields	Wrong equation for uniform vs radial	Parallel plates: E = V/d. Point charges: E = kQ/r²
Capacitors	Not converting μF to F	1 μF = 10⁻⁶ F — always convert before substituting
Nuclear physics	Confusing mass number and atomic number	Mass number (top) = protons + neutrons
Thermodynamics	Using °C instead of K	Gas law equations always need kelvin

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Paper 3: General and Practical Principles in Physics

• Duration: 2 hours 30 minutes
• Marks: 120
• Weighting: 40% of the total A-Level

Paper 3 is the longest and most challenging paper. It can draw on content from anywhere in the specification and includes questions that test practical skills in a written context. You will not perform experiments in the exam, but you will need to describe procedures, identify variables, calculate uncertainties, evaluate methods, and suggest improvements.

Paper 3 also includes synoptic questions that link different topic areas. For example, a question might combine energy conservation from mechanics with electric field calculations from fields, or link wave properties with quantum physics.

Paper 3 Strategy

Because Paper 3 covers everything, it is essential to have revised the full specification. Time management is critical: with 120 marks in 150 minutes, you have 1.25 minutes per mark. Do not spend too long on any single question. If you get stuck, move on and return to it later.

graph TD
    A["Paper 3: 150 min, 120 marks"] --> B["Section A: Multiple choice"]
    A --> C["Section B: Short & long answer"]
    A --> D["Practical-based questions throughout"]
    B --> E["~15 min allocation"]
    C --> F["~125 min allocation"]
    D --> G["Expect: describe procedure,\nidentify variables,\ncalculate uncertainties,\nevaluate methods"]
    F --> H["Synoptic questions linking\nmultiple topic areas"]
    H --> I["Example: energy conservation\n+ field calculations"]

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Paper Structure Comparison

Feature	Paper 1	Paper 2	Paper 3
Duration	1 h 45 min	1 h 45 min	2 h 30 min
Total marks	90	90	120
Weighting	30%	30%	40%
Minutes per mark	1.17	1.17	1.25
Content	Mechanics, circuits, materials, waves	Further mechanics, fields, nuclear, thermo	All topics + practical skills
Multiple choice	Yes	Yes	Yes
Extended response	Yes	Yes	Yes
Practical questions	Limited	Limited	Extensive
Synoptic questions	No	Limited	Yes

Use these figures to calculate how long you should spend on each question. A 5-mark question in Paper 1 deserves approximately 6 minutes. A 6-mark extended response in Paper 3 deserves approximately 7–8 minutes. Discipline with time allocation is one of the simplest ways to improve your overall grade.

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Assessment Objectives

All three papers assess three objectives:

• AO1 (Demonstrate knowledge): Recall and state facts, definitions, and equations. Worth approximately 29–31% of the total marks.
• AO2 (Apply knowledge): Use your knowledge to solve problems and explain phenomena. Worth approximately 34–36%.
• AO3 (Analyse and evaluate): Interpret data, evaluate methods, draw conclusions, and assess evidence. Worth approximately 34–36%.

AO2 and AO3 together account for roughly 70% of the marks. This means rote memorisation alone is not sufficient — you must practise applying your knowledge to unfamiliar problems and analysing experimental data.

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What the Data Sheet Does and Does Not Give You

The data sheet provided in every exam contains selected equations and physical constants. Knowing exactly what is on it — and what is not — prevents wasted revision time and avoids exam panic.

Given on data sheet	Must be memorised
E = hf	All SUVAT equations
λ = h/p (de Broglie)	v = fλ
Coulomb's law: F = kQ₁Q₂/r²	Ohm's law: V = IR
Gravitational field: g = GM/r²	Resistors in series and parallel
Capacitor energy: E = ½CV²	Kinetic energy: Ek = ½mv²
Radioactive decay: N = N₀e^(−λt)	GPE near surface: Ep = mgh
Ideal gas: pV = nRT	Power: P = IV = I²R = V²/R
Constants (c, h, e, G, k, etc.)	Definitions of field strength, potential, etc.

Practise without the data sheet to find out which equations you genuinely have memorised and which you have been unconsciously relying on having in front of you.

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Deeper Strategy: Understanding the Edexcel Physics Papers

Edexcel A-Level Physics (9PH0) is assessed through three written papers that, between them, span every topic on the specification, every Core Practical, and every kind of physics demand from one-mark recall to extended-response argument. The strategy that wins these papers is not "know more physics" — it is structured triage, disciplined unit work, and a clear-eyed sense of where each paper places its marks. The sections below break the assessment into a usable game plan.

Detailed structure

The 9PH0 specification splits content into 13 numbered topics and 16 Core Practicals. The three papers carve this content up unevenly, and that asymmetry has direct strategic consequences.

Paper	Code	Duration	Marks	Content
Paper 1: Advanced Physics I	9PH0/01	1h 45m	90	Topics 1-5: Mechanics, Electric Circuits, Materials, Waves, Particle Nature of Light
Paper 2: Advanced Physics II	9PH0/02	1h 45m	90	Topics 6-13: Further Mechanics, Electric and Magnetic Fields, Nuclear and Particle Physics, Thermodynamics, Space, Nuclear Radiation, Gravitational Fields, Oscillations
Paper 3: General and Practical Principles	9PH0/03	2h 30m	120	Synoptic across all 13 topics, plus the 16 Core Practicals

Each paper is sat in a single sitting with no choice of questions. All questions must be attempted. A scientific or graphical calculator is permitted in every paper, and a Pearson-issued data and formulae booklet sits alongside each paper containing constants, equations not given in the question stem, and the standard formulae you are not expected to memorise.

Paper 1 is recognisably "Year 1 plus Topic 5". The mechanics block (kinematics, dynamics, energy, momentum) typically anchors the front of the paper with short calculations, while waves and the particle nature of light tend to host the longer structured questions and at least one extended-response question on photoelectric or interference phenomena. Materials questions appear consistently and reward candidates who can read a stress-strain or force-extension graph cleanly.

Paper 2 is denser conceptually because it stacks the Year 2 abstract topics — fields, capacitance, oscillations, thermodynamics, particle physics — into the same 90-mark envelope. Expect a longer opening of short calculation questions, a middle band of structured 6-9 mark questions, and one or two extended-response questions on synoptic field-and-particle situations or astrophysical reasoning. Gravitational and electric field analogies often anchor a synoptic question that spans Topics 7 and 12.

Paper 3 is the longest paper and the least like a topic-test. Half the marks live in synoptic questions that draw together two or three different topic strands; the rest sit in practical-skills questions that test the 16 Core Practicals — graph drawing, uncertainty calculation, evaluation of method, identification of systematic error. There is no separate practical exam in Edexcel 9PH0; Paper 3 is where practical understanding is graded, and a candidate who has only read the Core Practicals rather than thought about them will lose marks here that no amount of theoretical knowledge can recover.

Question-by-question time budget

Across all three papers, the time-per-mark figure clusters tightly around 1.15-1.25 minutes. Anchor every pacing decision against this. A 105-minute paper at 90 marks gives a clean 1.17 min per mark; the 150-minute Paper 3 at 120 marks gives 1.25 min per mark. The marginally slacker pacing on Paper 3 is deliberate — practical questions take longer to read.

Mark value	Target time	Realistic upper bound	Typical question type
1 mark	1 min	1.5 min	Single recall, define a term, read a value off a graph
2 marks	2.5 min	3 min	One-step calculation with unit; short explanation
3 marks	3.5 min	4.5 min	Two-step calculation; brief explanation with reasoning
4 marks	5 min	6 min	Multi-step calculation; short structured derivation
5 marks	6 min	7.5 min	Calculation with rearrangement; explanation with two linked points
6 marks	7 min	9 min	Extended explanation, often "QWC" assessed; structured calculation with sub-parts
8 marks	10 min	12 min	Extended-response: explain a phenomenon, link two principles, evaluate evidence
10-12 marks	12-14.5 min	16-18 min	Synoptic Paper 3 question with practical and theoretical strands

The 6-mark question deserves a paragraph of its own. On Edexcel physics papers, a 6-mark question is rarely a calculation. It is almost always an explanation that asks you to link a sequence of physical principles to an observed phenomenon — for example, explain why the maximum kinetic energy of a photoelectron does not depend on the intensity of the incident light, or explain how the standing wave pattern on a stretched string changes as the driving frequency is increased. The marks are awarded for distinct correct points, each one supported by either a named principle, an equation, or a clearly stated cause-and-effect link. A candidate who writes a single dense paragraph typically scores 3 or 4; a candidate who writes six numbered points, each anchored to a principle, typically scores the full 6.

Extended-response (essay-style) questions worth 8 or more marks appear on all three papers, most reliably on Papers 2 and 3. They are signposted by demand verbs such as evaluate, discuss, explain how and why, or analyse. They are also the questions most often left blank or attempted in two scrappy lines. The route through them is to plan in the margin first: list four or five distinct physics points you intend to make, label each with the topic strand, and only then write. The plan costs 90 seconds and routinely raises the score by 3 or 4 marks.

High-yield content for this skill

The 13 specification topics do not weigh equally. Across recent papers the following content blocks consistently account for the largest share of marks, and these are the topics where revision time is most efficiently spent.

Topic block	Typical share	Common question types
Mechanics (kinematics, dynamics, energy, momentum)	25-35% of Paper 1	Projectile motion, force-balance, energy conversion, momentum conservation in collisions
Electric circuits	15-20% of Paper 1	EMF and internal resistance, potential dividers, resistor networks, I-V characteristics
Waves and the particle nature of light	20-30% of Paper 1	Diffraction gratings, double-slit interference, photoelectric calculations, photon energy
Fields (electric, magnetic, gravitational)	25-35% of Paper 2	Field strength and potential, comparison of inverse-square fields, charged-particle motion
Further mechanics and oscillations	15-25% of Paper 2	Circular motion, simple harmonic motion equations, energy in oscillating systems, resonance
Nuclear, particle and thermodynamics	20-30% of Paper 2	Decay equations, binding energy, ideal gas calculations, internal energy
Practical skills	30-40% of Paper 3	Uncertainty propagation, graph drawing, evaluation of method, identification of systematic vs random error
Synoptic combinations	30-40% of Paper 3	Field-with-circuit, oscillation-with-energy, nuclear-with-graph-analysis

The strategic implication is direct. A candidate who is fluent in mechanics, fields, and practical-skills questions has secured the route to a strong grade across all three papers. A candidate who has memorised only theory and not practised graph-and-uncertainty work will hit a ceiling on Paper 3 that no amount of late revision can break.

Worked walkthrough: a mock physics question

Specimen question modelled on the Edexcel 9PH0 paper format:

A student investigates the photoelectric effect using a clean zinc plate connected to a sensitive electroscope. Light of wavelength 250 nm is incident on the plate. The work function of zinc is 4.31 eV. (a) Calculate the maximum kinetic energy, in joules, of a photoelectron emitted from the plate. (3) (b) The intensity of the incident light is doubled. State and explain the effect, if any, on the maximum kinetic energy of the emitted photoelectrons. (3) (c) The wavelength of the incident light is increased to 320 nm. The student claims that no photoelectrons will be emitted. Determine whether the student is correct. (3)

Here is how a strong candidate would plan and execute.

Pre-plan sketch (30 seconds, in the margin): Before any algebra, the strong candidate notes the three relevant equations: photon energy $E = hf = hc/\lambda$E=hf=hc/λ, work function relationship $hf = \phi + KE_{\max}$hf=ϕ+KEmax​, threshold frequency $f_0 = \phi/h$f0​=ϕ/h. They also note the unit conversion: $1 \text{ eV} = 1.60 \times 10^{-19}$1 eV=1.60×10−19 J, so $\phi = 4.31 \times 1.60 \times 10^{-19} = 6.90 \times 10^{-19}$ϕ=4.31×1.60×10−19=6.90×10−19 J. This conversion is the easiest mark in the question to drop, so it is done first and ringed.

Plan (45 seconds in the margin): "(a) photon energy from $hc/\lambda$hc/λ; subtract work function; answer in J to 3 s.f. (b) intensity doesn't change KE; only frequency does. Explain via photon model. (c) find threshold wavelength; compare to 320 nm."

Part (a): Photon energy $E = \frac{hc}{\lambda} = \frac{(6.63 \times 10^{-34})(3.00 \times 10^{8})}{250 \times 10^{-9}} = 7.96 \times 10^{-19}$E=λhc​=250×10−9(6.63×10−34)(3.00×108)​=7.96×10−19 J. Maximum kinetic energy $KE_{\max} = E - \phi = 7.96 \times 10^{-19} - 6.90 \times 10^{-19} = 1.06 \times 10^{-19}$KEmax​=E−ϕ=7.96×10−19−6.90×10−19=1.06×10−19 J. State clearly: Maximum kinetic energy = $1.06 \times 10^{-19}$1.06×10−19 J (to 3 s.f.). Carrying exact values until the final line avoids compounded rounding.

Part (b): Doubling the intensity doubles the number of photons arriving per unit time but does not change the energy of each photon. Each photoelectron is liberated by absorbing one photon, so the maximum kinetic energy of the emitted photoelectrons is unchanged. Three distinct points scored: (i) intensity affects photon number, not energy; (ii) one-photon-one-electron interaction; (iii) explicit conclusion that $KE_{\max}$KEmax​ is unchanged.

Part (c): Threshold wavelength $\lambda_0 = \frac{hc}{\phi} = \frac{(6.63 \times 10^{-34})(3.00 \times 10^{8})}{6.90 \times 10^{-19}} = 2.88 \times 10^{-7}$λ0​=ϕhc​=6.90×10−19(6.63×10−34)(3.00×108)​=2.88×10−7 m $= 288$=288 nm. Since 320 nm is greater than the threshold wavelength of 288 nm, the photon energy at 320 nm is less than the work function, and no photoelectrons will be emitted. The student is correct. State the comparison explicitly — examiners reward the because 320 > 288 sentence as much as the calculation that produces 288.

Sanity-check at the end: The candidate adds 45 seconds to confirm the unit conversion eV-to-J, verifies the order of magnitude on $KE_{\max}$KEmax​ (around $10^{-19}$10−19 J is right for visible-UV photoelectrons), and re-reads the demand verbs to confirm each part has been answered with the right structure (calculate, state and explain, determine).

Common Paper 1/2/3 pitfalls

1. Significant figures sloppiness. Edexcel typically expects answers to 2 or 3 s.f., matching the data given. Quoting $1.0625 \times 10^{-19}$1.0625×10−19 J when the input data is given to 3 s.f. is a forfeited A-mark every time. Read the data first and let it set the precision.
2. Unit conversion at the data stage. Lengths given in mm, cm, or km must be converted to metres before substituting into an equation. The single most common mark loss on mechanics calculations is treating a 25 mm extension as 25 m.
3. Sign errors in field and momentum work. Direction matters. A momentum-conservation calculation involving a rebound must treat the initial and final velocities with opposite signs. State your sign convention at the top of the working.
4. Calculator radian/degree mode. Simple harmonic motion calculations involving $\cos(\omega t)$cos(ωt) and circular-motion calculations involving angular velocity must be done in radians. Switch the calculator at the start of the paper and write RAD in the margin to remind yourself.
5. Missing graph axes labels and units. A graph drawn for a Paper 3 practical-skills question scores marks for axis labels with units, sensible scales using more than half the printed grid, plotted points to within half a small square, and a best-fit line drawn with a clear ruler. Skipping any one of these forfeits a mark independently.
6. Blank-page extended response. A 6 or 8-mark extended-response question left blank or with a single sentence is the largest avoidable loss in the paper. Even a partial plan with three labelled points typically scores 2 or 3 marks. Always commit something to the page.
7. Mis-applying $W = mg$W=mg as $W = m$W=m. Weight is a force, mass is a quantity. The numerical answer for weight in newtons is roughly ten times the mass in kilograms — a useful sanity check. Forgetting the factor of $g$g is a recurring slip on mechanics warm-ups.
8. Treating internal resistance as zero. When a question gives an EMF and an internal resistance, the terminal potential difference is $V = \varepsilon - Ir$V=ε−Ir, not $V = \varepsilon$V=ε. Read the circuit diagram for the internal-resistance symbol before calculating.
9. Confusing $f$f and $\omega$ω in oscillations. Angular frequency $\omega = 2\pi f$ω=2πf enters the SHM equations, not the linear frequency $f$f in hertz. A factor-of-$2\pi$2π error here cascades through every subsequent line.
10. Mis-reading "exact" or "in terms of $\pi$π". When a question asks for an exact answer or one in terms of $\pi$π, a decimal approximation forfeits the A-mark even when the value is correct. Read the demand verb on the final line of each part.
11. Skipping the data and formulae booklet check. Several constants and equations are provided in the booklet and do not need to be memorised. Quoting them from memory introduces avoidable errors. Before each paper, spend two minutes locating the constants you most often use.

Mark-scheme phrasing patterns

Edexcel mark schemes use three letter-codes that determine where marks live: M (method), A (accuracy), and B (independent). Understanding what each rewards changes how you write your answers.

M-marks are awarded for choosing and applying a correct method, even if the final number is wrong. This is why showing your working matters: a clearly stated substitution into $F = BIL$F=BIL earns the M-mark even if you make an arithmetic slip in the final line. Examiners look for evidence such as the equation being quoted before substitution, the substituted values being visible (with units where appropriate), and the rearrangement to make the required quantity the subject. On a 3-mark calculation it is typical to see M1 (correct equation and substitution), M1 (correct rearrangement or further step), A1 (correct final answer with unit and appropriate s.f.).

A-marks depend on a previous M-mark — they are awarded for accuracy given the right method. Final answers in the form requested (with the right unit, the right number of significant figures, and the right sign) secure the A-mark. An A-mark is forfeited if the answer is correct numerically but lacks a unit, or is given to 5 s.f. when the data only justifies 3.

B-marks are independent — awarded for a stand-alone correct fact or value. Stating that a wave is transverse, that a beta-minus particle is an electron, that the unit of magnetic flux density is the tesla, or that a damping force opposes motion, can each earn a B-mark without supporting working. Do not skip these — they are the cheapest marks on the paper, and they cannot be lost by an arithmetic slip elsewhere.

The crucial distinction between M1 and B1 is dependency. An M1 lives inside a chain of working and can be lost if the working is fragmented or unrecognisable. A B1 is atomic — awarded for a correct standalone statement regardless of surrounding work. Practically, this means: if a question asks you to state and explain a phenomenon, the state portion typically carries a B-mark and the explain portion the M-marks. Never leave a state half blank because you "don't have working to show". The standalone correct statement is the work.

Presentation conventions matter on physics scripts. Write each step on a new line. Quote the equation in symbols before substituting numbers. Carry units through every line of working, not just the final answer. Box or underline each final numerical answer. On extended-response questions, number your physics points so the examiner can match them to the mark scheme without re-reading. Examiners mark hundreds of scripts under time pressure — a clean script earns the benefit of the doubt; a chaotic one does not.

Going further — pre-exam preparation

• Final week strategy: Sit one full past paper under exam conditions every other day, alternating with a focused topic-revision day. Mark your own paper using the official mark scheme, and log every lost mark in a "leak list" — patterns will emerge within three papers.
• Use the leak list. If you keep losing marks on capacitor-discharge calculations, devote 45 minutes to drilling 8-10 such questions back-to-back. Pattern recognition beats general revision in the final week.
• Calculator drills. Practise switching between radian and degree modes, evaluating exponentials and logarithms cleanly, using the calculator memory for repeated constants, and entering numbers in scientific notation without rounding mid-step. Five minutes a day for two weeks is enough to make the calculator second-nature.
• Core Practical drill. Walk through each of the 16 Core Practicals from memory: equipment list, procedure in five bullets, the variable graphed against which, the expected shape, the dominant source of uncertainty, and one realistic improvement to the method. If you cannot do this for any practical, that is your highest-priority Paper 3 revision task.
• BPhO and IPhO extension. Candidates targeting Cambridge, Imperial, or other physics-heavy destinations should spend the final 4-6 weeks working on British Physics Olympiad (BPhO) Round 1 questions alongside A-Level revision. The BPhO rewards the same skills 9PH0 rewards — modelling, dimensional analysis, careful unit work — but in less-scaffolded form. One BPhO question every other day for two months transforms A-Level performance. International Physics Olympiad (IPhO) problems are a stretch beyond this and are appropriate only for candidates already comfortable with BPhO Round 2.
• Sleep, not cramming. The night before each paper, review your leak list for 30 minutes, pack your kit (calculator with fresh batteries, spare calculator if permitted, a clear ruler, a sharp pencil, a protractor for any practical-skills graph work), and sleep. Marginal extra revision after 9pm is destroyed by lost sleep — and physics calculations done on a tired brain are particularly error-prone.

Edexcel alignment footer

This content is aligned with the Pearson Edexcel GCE A Level Physics (9PH0) specification, Papers 1, 2 and 3. For the most accurate and up-to-date information, please refer to the official Pearson Edexcel specification document.

Visual summary

graph TD
  A["Read question stem<br/>(60-90 seconds)"] --> B["Identify topic strand<br/>(mechanics / fields / waves / etc)"]
  B --> C["Note marks and<br/>demand verbs"]
  C --> D{"Time budget:<br/>~1.2 min per mark"}
  D --> E["Convert units<br/>at the data stage"]
  E --> F["Quote equation<br/>before substituting"]
  F --> G["Execute cleanly,<br/>carry units through"]
  G --> H{"Stuck past<br/>1.5x budget?"}
  H -- "Yes" --> I["Mark with star,<br/>move on"]
  H -- "No" --> J["Box final answer<br/>with unit and s.f."]
  I --> K["Continue paper"]
  J --> K
  K --> L{"All questions<br/>attempted?"}
  L -- "No" --> A
  L -- "Yes" --> M["Return to starred<br/>questions"]
  M --> N["Final 8-12 min:<br/>check units, signs, s.f."]
  N --> O["Verify graph labels<br/>and extended-response plans"]
  O --> P["Submit"]