Overview
For the IB Diploma Programme, paper 2 is the paper where technique, not knowledge, decides your grade. It is the structured and extended-response paper, marked point by point, and the golden rule for almost every calculation is the same: write the equation, show the substitution, then state the answer with its unit. Do that consistently and you bank method marks even when your arithmetic slips — miss it and you leave marks on the table you had already earned. This guide breaks down exactly how the marking works and how to write answers that collect every available point.
How Paper 2 is marked — method, accuracy, ECF
For the IB Diploma Programme, paper 2 is marked analytically, meaning each question is split into individual marking points rather than judged as a whole. Those points come in two flavours:
- Method (M) marks reward the correct approach — choosing the right equation from the data booklet, rearranging it correctly, and substituting the right quantities.
- Accuracy (A) marks reward the correct final value, quoted with the right unit and a sensible number of significant figures.
The crucial consequence is error-carried-forward (ECF). If you get a wrong number early on but then use that wrong number correctly in a later part, the later method marks are still yours. A miscalculated velocity in part (a) does not have to sink part (b).
Here is what that looks like in practice. Suppose a question asks you to find a car's acceleration, and you have (wrongly) worked out a final velocity of 25 m s⁻¹ instead of 20 m s⁻¹ in the previous part. You then write:
a = (v − u) / t = (25 − 5) / 4 = 5.0 m s⁻²
The number is wrong because your v was wrong upstream — but the examiner can see you chose the right equation and substituted correctly, so the method mark is awarded under ECF. Write only "5.0 m s⁻²" with no working and the examiner sees a wrong answer with nothing to credit: zero. Same number, completely different score. Working is what makes ECF possible.
The equation → substitution → answer layout that banks method marks
For the IB Diploma Programme, train yourself into a three-line habit for every calculation worth more than one mark:
- Equation — write it in symbols exactly as it appears in the data booklet.
- Substitution — put the numbers in, with units, before you touch your calculator.
- Answer — the final value, rounded once, with the correct unit.
This layout forces you to commit to a method (the M mark), creates a visible substitution line the examiner can credit even if the answer is wrong, and stops you doing algebra in your head where mistakes hide. Never collapse a multi-mark part into a single number — it is the most common way strong students quietly lose marks.
Units, significant figures and direction — the avoidable losses
For the IB Diploma Programme, these are pure technique marks, and they are the ones that separate a 5 from a 7 because none of them require extra physics knowledge.
- Units. An accuracy mark frequently requires the correct unit. A bare number can lose it outright. Write the unit on every final answer, and watch prefixes — kJ is not J, MeV is not eV.
- Significant figures. Quote answers to a sensible precision, usually matching the least precise data (typically 2–3 sig figs). Rounding too early or quoting ten digits both cost accuracy marks. Carry full precision through your working and round only at the very end.
- Direction. Physics is full of vectors. When a question says "state the magnitude and direction of the force" or "the velocity," a magnitude alone is half an answer. Name the direction explicitly — "downwards," "to the left," "towards the centre."
"Show that" and command terms decoded
For the IB Diploma Programme, "Show that" questions give you the answer — for example, "show that the acceleration is approximately 9.8 m s⁻²." The trap is subtle: because the target value is printed, you must work to more precision than the given figure to prove you derived it rather than copied it. If the question says "≈ 9.8," carry your working to 9.81 or 9.813. Show every substitution; a "show that" with no working scores nothing even with the right final number.
The command term at the start of each part tells you the type of response required, and mismatching it is a silent mark-killer:
- State / define — a concise, precise recall answer. No essay, but no vagueness.
- Explain — give the physics reason, a causal chain linked to a principle, not just a description of what happens.
- Determine / calculate — a numerical answer with working shown.
- Sketch — a graph with the correct shape and key features (intercepts, gradients, asymptotes) — not a plotted, to-scale graph.
Learn these cold; our IB command terms explained guide lists them all.
Graphs, gradients and uncertainties
For the IB Diploma Programme, data-handling parts recur in almost every Paper 2, and they reward precision:
- Read gradients off the best-fit line, not two raw data points. Pick two points that lie on your line, spread far apart, and quote the gradient with its unit. Often it equals a physical quantity — a spring constant, resistance or rate — so state what it represents rather than leaving a bare number.
- Uncertainties. Combine absolute and percentage uncertainties correctly, draw and use error bars, and find maximum/minimum gradient lines when asked. These questions separate 6s from 7s, so drill them deliberately.
Explanation questions — give the physics reason
For the IB Diploma Programme, not every mark is a calculation. An explain part wants the mechanism. Compare two answers to "explain why a satellite in a lower orbit moves faster":
- Weak: "because gravity is stronger lower down." (Describes, does not explain.)
- Strong: "the gravitational force provides the centripetal force; closer to the planet this force is larger, so a greater orbital speed is required to maintain the orbit."
The strong answer names the principle and follows the causal chain. Use the exact phrasing the mark scheme expects — "the resultant force," "the induced EMF opposes the change" — as near-synonyms often miss the marking point.
Using the data booklet efficiently
Every candidate gets the same booklet of equations and constants, so the edge is fluency, not memory. Knowing roughly *where* each equation lives — kinematics, fields, circuits, nuclear — lets you flip straight to it instead of hunting mid-exam. Practise every past question with the booklet open until finding the right equation is automatic. The booklet gives you the formula, but never tells you *which* one applies or how to rearrange it — that judgement is what practice builds. Our free [IB Physics SL course](/ib/courses/physics-sl) and [HL course](/ib/courses/physics-hl) map every syllabus point to a lesson so you can close gaps fast.
High-frequency areas worth over-practising: kinematics and SUVAT, forces and momentum, energy and power, circuits, fields, waves, and nuclear calculations — plus the graph, gradient and uncertainty questions that thread through them all.
Common mistakes that cap you at a 5
For the IB Diploma Programme, none of these are about knowing less physics. They are the leaks that stop good candidates reaching a 7.
- No working shown — forfeits method marks and blocks ECF entirely.
- Missing or wrong units on the final answer.
- Sloppy significant figures or rounding mid-calculation.
- Dropping direction on a vector quantity.
- Radian/degree calculator mode slips that wreck wave, oscillation and circular-motion answers.
- Answering the wrong command term — calculating when asked to explain, or writing an essay when asked to state.
How MarkScheme helps you practise and get marked
Self-marking is essential but has a ceiling — it is hard to judge your own extended answers the way an examiner would. After a past paper, [get your answer marked](/mark) against the criteria to see exactly which M and A marks you banked and which you left behind. Pair that with the [SL past papers](/blog/ib-physics-sl-past-papers-guide) guide for timed practice, the broader [how to get a 7 in IB Physics](/blog/ib-physics-how-to-get-a-7) strategy, and the [IB guides hub](/guides/ib) for everything else.
Frequently asked questions
This section covers Frequently asked questions — what IB examiners reward most often in past papers and coursework.
What are ECF marks in IB Physics?
ECF stands for error-carried-forward. If you make a mistake in one part but use your (wrong) value correctly in a later part, the examiner still awards the method marks in that later part — provided your working is visible. It means a single slip does not cascade through a whole question.
Do I lose marks for units?
Yes. Many accuracy marks explicitly require the correct unit, so a bare number can lose the mark even when the value is right. Write the unit on every final answer and watch your prefixes (kJ vs J, MeV vs eV).
How much working should I show on Paper 2?
For any multi-mark or "show that" part: the equation, the substitution, then the answer. Examiners can only award method marks and apply ECF for reasoning they can actually see on the page.
What does "show that" require?
Work to more precision than the given value to prove you derived it, and show every substitution. A "show that" with only the final (printed) number and no working scores nothing.
How is Paper 2 different from Paper 1?
Paper 2 is the structured and extended-response paper, marked point by point with method and accuracy marks and ECF. Paper 1 includes multiple-choice questions scored right or wrong with no credit for working, so Paper 2 is where visible technique pays off most.