How marks are actually earned

critique-the-model-answer-not-connected-to-the-stated-model

Confirmed verbatim, and the only real past-paper anchor spec 1.1 has as a standalone question type: "Candidates need to appreciate that the question refers to 'the model' and the model is clearly described in the second paragraph of the question. Hence only modifications to that model received credit" (Oct 2019, Q6). A true-sounding statement about the real world — however scientifically accurate — earns nothing if it isn't a relaxation of a simplification the question's own stated model actually named. Find the sentence that states the trade-off before answering, not after.

show-that-final-value-stated-without-the-full-explanation

Examiner reports across at least five series (Jan 2020, Jan 2023, Oct 2022, Jun 2024, Oct 2023) each repeat some form of the same standing instruction: "when a question asks candidates to 'hence show that', ... a full explanation, including all steps, is required to earn full marks, where the explanation must use one or more of the previous parts of the question." On an ag part, the printed target being reached is not, by itself, evidence of anything — a candidate could read it straight off the page. The marks are for the shown argument that arrives there, using a previous part's own value, not for the number matching.

modelling-term-treated-as-decorative-rather-than-load-bearing

A related trap confirmed on a rod-modelling question: "There was general appreciation that modelling the beam as a rod meant that it did not bend, [but] some candidates failed to achieve the mark for including wrong or irrelevant extra statements. The most common incorrect answers related to the mass (or centre of mass) of the rod and comments such as 'clockwise moments equal anticlockwise moments'" (Jan 2020, Q2(b)). "Clockwise moments equal anticlockwise moments" is the EQUILIBRIUM CONDITION, not a consequence of the rod-modelling term — it would be true whatever object the beam had been modelled as. Every term in spec 1.1's vocabulary list licenses a specific, nameable consequence (see the teach block above); a question asking what a modelling term assumes wants THAT consequence, not the technique used to solve the rest of the question.

bearing-sin-cos-pairing-swapped

Confirmed directly on a real bearing-to-vector question: "a significant number showed a lack of knowledge of bearings and an answer of 12i + 16j was often seen" — the report is explicit that "the correct conversion required swapping the components" (Jun 2024, Q7). The mechanism is treating a bearing (measured clockwise from NORTH) like a standard angle (measured anticlockwise from EAST), which swaps which axis sine belongs to. The marked-solution block above reconstructs this exact wrong answer with real, checkable numbers.

triangle-of-forces-supplement-not-taken

Confirmed on a real resultant-of-two-forces question that directly compared the two standard methods: "those candidates who resolved in two perpendicular directions and then used Pythagoras tended to have more success than those who attempted to use the cosine rule on a triangle of forces. A common error with this approach was to use an incorrect angle of 30, 60 or in some cases 330 degrees, even when they had drawn what appeared to be the correct obtuse angled triangle" (Jun 2024, Q2). The triangle itself being right and the angle plugged into the formula being wrong is precisely the failure mode a correct sketch does not, by itself, protect against — the interior angle at the shared vertex is the SUPPLEMENT of the angle between the forces as drawn from their common point, never that angle directly.

incomplete-resolution-missing-a-term

Confirmed on a real equilibrium/resolving question, where a candidate resolved in one direction but dropped a whole force from the equation: "incomplete resolutions e.g. 5 = Fcos30 rather than 5 = Fcos30 + Tcos60" (Jan 2022, Q1, the same series and question that independently confirms Lami's theorem as a credited alternative method — "another direct method involved applying Lami's theorem"). This is a method error, not an accuracy error, under the mark scheme's own general principles for Mechanics marking: an equation produced by resolving is only creditable once every force with a component in that direction has actually been multiplied by its own sin or cos and included — one omitted term breaks the method mark, whatever the rest of the arithmetic does afterwards.

two-stage-motion-treated-as-a-single-suvat-equation

The dominant trap in this whole topic, independently confirmed in at least two series. Jan 2023 Q5, a vehicle in two distinct phases of acceleration: "many failed to appreciate that they needed to consider two stages of the motion and tried to use t = 14 in a single suvat equation thereby achieving no credit." Jun 2024 Q5, a box falling from a helicopter and then decelerating under a parachute: "a very small number of candidates failed to realise there were two distinct stages of the motion and used an acceleration of 9.8 ms⁻² throughout," and separately, "the most common [error], assuming that the box was accelerating rather than decelerating." Two different series, two different physical scenarios, the same underlying failure: an acceleration valid for only part of a journey, applied as if it held for the whole thing.

halved-the-deceleration-time-instead-of-doubling-it

Verified on the real "acceleration, constant speed, deceleration over unknown time $T$" graph question that anchors much of this topic: "a common error was to halve the time taken to decelerate rather than double it" (Jan 2023, Q1). Whatever ratio a question states between two time intervals — one phase taking twice, or three times, as long as another — the arithmetic has to go the direction the stem actually describes; a plausible-looking number produced by inverting that ratio is still wrong.

same-time-variable-reused-across-different-start-times

Verified on a "two particles released at different times" question (Jan 2020, Q3): "some candidates wrote down two correct expressions for the displacements but failed to realise that they referred to different starting times which led to inconsistent values of t." Each individual displacement expression can be entirely correct in isolation and the question can still fail at the moment they're set equal, if one particle's clock and the other's haven't been reconciled first — a later-released particle needs its own time variable, or the earlier one's time variable shifted by the head start, before the two expressions can be honestly compared.

quadratic-root-rejected-without-justification

Verified on a question where solving a suvat-derived quadratic left two roots, only one of them physically valid: "the vast majority found the two roots but some failed to explain clearly why they were rejecting 50" (Oct 2019, Q6), and separately, "candidates need to be reminded to show working when solving quadratics as those who had not derived the correct equation sometimes just wrote down an incorrect answer and received no credit." A kinematics quadratic's two roots are not automatically two valid answers — one can sit outside the time interval the model actually describes (e.g. after the particle has already stopped) — and finding both roots is only half the question; the other half is a stated reason for discarding the one that doesn't fit.

vector-equation-solved-as-if-it-were-one-scalar-equation

WME01-verified-facts.md's one verified real-paper fact for this exact spec point (Jan 2022 Q6) mostly names the CORRECT technique, not a documented wrong one — the record is that candidates 'equated coefficients of i and j to find the values of p and q.' The same examiner-report sentence this is drawn from does go on to name one further error too ('a few neglected to include m or subtracted rather than added the forces'), but Pearson's own examiner describes it as rare, with no numbers and no second series confirming it — thin enough that this lesson still builds its trap-taxonomy mostly around the correct technique's own implication rather than that one rare note (see the closing flag block for the full accounting). But the phrase names the trap by implication: a vector equation like $p\mathbf{i}+q\mathbf{j}=12\mathbf{i}+8\mathbf{j}$ is not one equation with two unknowns solved together — it is two entirely independent equations, $p=12$ and $q=8$, that happen to be written on one line. Treating it as a single combined equation (adding $p+q$, or hunting for one 'resultant' unknown that covers both) has no valid method behind it — the mechanism block above shows why i and j being independent directions makes 'equate coefficients separately' the only route in, not one option among several.

mass-omitted-from-the-vector-equation-of-motion

Not specific to this exact spec point in WME01-verified-facts.md's own summary, but a real, verified, general Mechanics-marking principle that applies to it directly: the mark scheme's own general principles for Mechanics marking state plainly, "Omission of mass from a resolution is a method error" (verified, identical wording across MS_Jan2023/MS_Jan2024/MS_Oct2023's general marking guidance). This principle is also independently corroborated as spec-4.1-specific by the real Jan 2022 Q6 examiner report itself — checked directly against the primary Pearson PDF during this lesson's review pass, its full sentence on part (a) reads "a few neglected to include m or subtracted rather than added the forces, but such instances were rare" — real evidence for this exact spec point, just low-frequency rather than a fully worked trap. Newton's second law in vector form is $\mathbf{F}=m\mathbf{a}$, not $\mathbf{F}=\mathbf{a}$ — silently dropping the mass, whether because it "looks like" it cancels or because a is mistaken for the resultant force directly, produces an equation that only happens to be correct when $m=1$. The marked-solution above reconstructs exactly this error and shows the real M0 consequence it carries.

newtons-second-law-applied-to-one-force-instead-of-the-resultant

Also a reasonable extension rather than a documented instance specific to this spec point: spec 4.1's own guidance pairs Newton's second law directly with spec 2.1/2.2's vector-addition content, and the most basic way to misapply $\mathbf{F}=m\mathbf{a}$ when more than one force acts is to substitute just one of the forces present, as though the other force weren't there. The worked-chain above builds its very first stage entirely around catching this before any arithmetic starts, for exactly this reason.

car-trailer-weight-components-dropped

Verified on a real car-and-trailer question on an incline: "the most common mistake was omission of the weight components which, if done consistently, fortuitously led to a correct value of D but this received no credit due to the missing terms in the two equations" (Oct 2019, Q3). The word "fortuitously" is doing real work — dropping both weight components in a consistent way can make two errors cancel and still produce a plausible-looking final number, which is exactly why a mark scheme built from M/A/B codes checks that every term that should be in an equation is actually there, independent of whether the final number happens to come out right.

peg-pulley-unfamiliar-two-tension-terms

Verified on a real two-tension peg/pulley question: "many seemed unfamiliar with this type of situation involving two tensions" (Jun 2024, Q3), with the specific error named as "including an extra 3mg term in their system equation of motion or for missing the 3mg term when giving the equation for Q." The fix the same report names directly: "drawing a separate diagram for each of P and Q would have helped some candidates to set up these equations correctly."

peg-pulley-given-tension-substituted-wrong-place

Verified on the same question: "some responses showed confusion between the T value given and the T value to be found, resulting in the substitution of T = 3mg into the wrong place" (Jun 2024, Q3). Two different unknowns sharing the letter T — or a value of T handed to you partway through a multi-part question, then needed again for something new — is a labelling trap as much as a mechanics one: rename a value the moment it stops being unknown, rather than letting one symbol carry two different meanings.

lift-mass-of-lift-alone

Verified: candidates "using the mass of the lift alone... instead of the whole-system" mass when writing the equation of motion for a lift carrying occupants (Jan 2023, Q7).

lift-occupant-reactions-omitted

Verified, the same family of error seen from the other equation: "many candidates attempted an equation of motion for the lift but omitted the reactions from the two occupants" (Oct 2022, Q4). Confirmed as a repeat Pearson question type across two separate series, not a one-off — and, worked through with real numbers, both versions of the mistake collapse onto exactly the same missing terms (see the marked solution above).

incline-friction-direction-reversed

Verified, the single most consistently reported error on this exact rough-incline scenario type: "the most common error was having the frictional force acting down rather than up the plane" (Oct 2022, Q3). Friction opposes actual (or impending) relative motion — never gravity, never "the picture" — so its direction is the one force on an incline diagram that has to be reasoned out LAST, after the direction of motion is already settled, not drawn first out of habit.

incline-changed-acceleration-not-recognised

Verified on a two-part incline question where the force condition changed between parts: "a substantial number did not recognise that the system was subject to a different acceleration" in the second part (Jun 2024, Q6). An acceleration found in an earlier part of a question is not a constant carried forward automatically — any change to a force in the system (a different driving force, friction switching on or off, a changed angle) generally means a genuinely new equation of motion and a genuinely new value of a, exactly the discipline spec 4.2(ii)'s own guidance — a force which changes from one fixed value to another — is testing directly.

velocity-sign-carried-into-speed-answer

The single strongest, most independently confirmed trap anywhere in the WME01 examiner-report record — verified across three separate series, not one. Jan 2020: "the most common error was in not taking account of the direction of the velocity and so not producing a positive answer as required for the 'speed' of P." Oct 2022: "candidates need to be reminded that the final answer needed to be positive as speed was required." Jun 2024: "the final mark was often lost because it had been left as negative." All three describe the same failure: the working is correct up to and including a genuinely negative velocity, and the final mark is lost only by copying that sign into an answer the question specifically called a speed. The fix costs one line: take the magnitude, and state the direction in words if the question wants it too.

harder-particle-chosen-for-impulse

Confirmed on a real WME01 impulse question: "the majority of responses used particle A to find the impulse, rather than using particle B which was much easier since it started at rest" (Jun 2024, Q1). This isn't a correctness error — both routes reach the same right answer — but it is a genuine, examiner-documented efficiency cost: computing the impulse via the harder particle first, then having to invoke Newton's third law to flip the result onto the particle actually asked about, is an extra step with its own extra chance to drop a sign, for no extra credit. Before substituting anything, check which of the two particles in the question has the simpler known velocities (often, but not only, the one that started at rest) and start there.

frictional-force-direction-reversed-on-a-rough-plane

Confirmed directly on a real rough-incline question: "the most common error was having the frictional force acting down rather than up the plane" (Oct 2022, Q3). Friction opposes the ACTUAL direction of relative sliding (or, in equilibrium, the direction the particle would tend to slide if friction vanished) — never the direction of an applied force, never "the direction the question feels like it should be," and never assumed from habit built up on simpler questions. This lesson's diagram and worked-chain both build their scenarios specifically so the correct direction is up the plane, deliberately reproducing the exact case this report documents students getting backwards.

changed-force-condition-assumed-not-to-change-the-acceleration

Confirmed on a real two-part incline question where a force condition changed between parts: "a substantial number did not recognise that the system was subject to a different acceleration" (Jun 2024, Q6). A particle continuing to move in the SAME direction across two parts of a question is not evidence that its acceleration is unchanged — if any force in the system has changed (a force added, removed, or altered in size), Newton's second law along the plane has to be rebuilt from scratch for that new part, never inherited from an earlier one. The marked-solution above reproduces this exact failure mode with real, checkable numbers, specifically chosen so the two accelerations really are different (not just relabelled).

equilibrium-and-limiting-motion-treated-as-two-unrelated-topics

Not a quoted student error from a mark scheme — this is the facts bank's OWN inference from the pattern across the archive (WME01-verified-facts.md §4, §7), named here as a trap because treating 4.4 and 5.3 as two disconnected spec items is the single easiest way to miss it: "Pearson's own question-writing treats statics of a particle on a rough plane and dynamics of a particle on a rough plane as the same scenario family split by whether acceleration is zero or not" — and the facts bank is explicit that this claim is "an inference from the pattern across the archive, not a fact stated anywhere in the spec text itself" (§7), not something Pearson has printed as a rule. Revising 4.4 and 5.3 as two separate equations to memorise, rather than as one resolving process with one variable outcome (does the along-plane resultant equal zero, or ma?), is the mechanism-level version of the direction and different-acceleration traps above — all three come from treating a rough-plane scenario as more disconnected from its own physics than it actually is.

incomplete-resolution-missing-a-term

The one trap this lesson is built around, verified in exactly one series — worth stating that plainly, since three-force equilibrium is a small enough topic in the archive reviewed for this course that inflating "one series" into "commonly" would misrepresent the evidence. A real WME01 mark scheme records: "incomplete resolutions e.g. 5 = Fcos30 rather than 5 = Fcos30 + Tcos60" (Jan 2022, Q1). The mechanism is structural, not a one-off slip: a resolution equation is only a correct description of the system once EVERY force with a component in the resolved direction has contributed its own term, each multiplied by the cosine (or sine) of its own angle to that direction — and the real general marking guidance treats an equation missing a term as a METHOD error (M0), not merely a wrong final number, because the equation itself describes a different, incomplete system. This lesson's diagram, method-comparison and marked-solution blocks all use the SAME scenario specifically so the correct equation (5 = Fcos30° + Tcos60°) and the documented wrong one (5 = Fcos30°) sit side by side, reproducing the real fragment's exact shape rather than a generic warning about "being careful."

wrong-reaction-zeroed-at-a-tilting-point

Confirmed verbatim, and the strongest single finding in this spec item's record: "it was necessary to appreciate that 'about to tilt' implied that one of the reactions had to be zero... A number of candidates equated the wrong reaction to zero i.e., in the case where the beam was about to tilt around C they assumed the reaction at C to be zero" (Jan 2023, Q4). The named pivot is the support that STAYS in contact; the reaction that vanishes belongs to the OTHER support. Say out loud which support is losing contact before writing anything as zero.

two-moments-equations-instead-of-moments-plus-resolve

Confirmed independently in two series. Jun 2024 Q4: "those that took moments about a different point required two equations to solve the problem and this inevitably led to more errors being made." Oct 2023 Q1, describing the successful approach by contrast: "Successful candidates then took moments about a number of different points to find the size of x... Where two moments equations were used, there was more opportunity for these errors." One support-point moment equation plus one resolve equation is (almost) always enough for two unknown reactions; reaching for a second moments equation is the sign a support point was not used the first time.

efficient-pivot-choice-explicitly-rewarded

The positive form of the same finding, confirmed in Jun 2024 Q4: "many realised that the smallest value of M would mean that the rod was about to tilt about C and therefore took moments about C. This produced an equation with M as the only unknown." Three series (Jan 2023, Jun 2024, Oct 2023) all reward the identical technique — take moments about the support whose reaction is already known (or about to become) zero, and the target unknown is left standing alone.

misread-relationship-between-two-given-unknowns

A related trap on the same spec item, from a rod held by two tensions rather than resting on two supports (the same technique — two unknown parallel forces along a rod, found by moments — applies either way): "the main errors were in the misinterpretation of the given information about the tensions. The tension at C was 20 N greater than the tension at A. However, pairs of values such as T and 20T, T and 20, or T and T were all seen on occasion" (Jan 2020, Q2). Before setting up any equation, write down in words what the stem's relationship between the two unknowns actually says — "20 more than," not "20 times."

modelling-assumption-confused-with-the-equilibrium-condition

"There was general appreciation that modelling the beam as a rod meant that it did not bend, [but] some candidates failed to achieve the mark for including wrong or irrelevant extra statements. The most common incorrect answers related to the mass (or centre of mass) of the rod and comments such as 'clockwise moments equal anticlockwise moments'" (Jan 2020, Q2(b)). "Clockwise moments equal anticlockwise moments" is the EQUILIBRIUM CONDITION, not a consequence of modelling the beam as a rod — it would be true (or not) whatever object the beam was modelled as. A question asking what the rod-model assumes is asking about rigidity and mass distribution, not restating the technique used to solve the rest of the question.