Technique Masterclasses

Mechanics 1

Flashcard Bank

Provenance: written 2026-09-29. This document is a reformatting exercise, not new research. Every flashcard below is a front/back reformatting of a sentence, formula, table row, or worked micro-example already present in the ten existing CODEX files in this folder: codex-formula-and-method-bank.md, codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md, codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md, codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md, codex-deep-dive-connected-particles-pulleys-and-lifts.md, codex-deep-dive-modelling-assumptions-and-show-that-discipline.md, codex-deep-dive-moments-rods-on-two-pivots.md, codex-deep-dive-momentum-impulse-sign-convention.md, codex-deep-dive-newtons-second-law-in-vector-form.md, codex-deep-dive-resultant-forces-and-bearings.md, and codex-complete-worked-paper.md. No new claim, formula, percentage, grade boundary, or exam finding is introduced here — every card's back is traceable to a real sentence, table row, formula, or worked value in one of those files, cited by document and section after each card. Quotations from a Pearson mark scheme or examiner report are kept under 15 words with attribution, exactly as the source CODEX files themselves quote them; everything longer is paraphrased. Where a source document itself flags a fact as unverified, inferred, or a genuine gap, this document repeats that same hedge rather than upgrading it to a plain fact.

CODEX · WME01 Flashcard Bank

Pearson Edexcel IAL Mechanics 1 (WME01/01)

One flashcard per term or result — front (the term, formula, or question), then back (the real definition, formula, or worked micro-example), organised by spec topic. Cards are numbered FC-001 upward for reference. Nothing below is a full worked exemplar; several cards point to a real exam anchor by series/question rather than reproducing its full working, since that full working already lives in the cited CODEX file.

Contents

Section 0 — Exam-wide conventions (apply across every topic)

FC-001 — Front: What value of g must be used in every WME01 calculation? Back: g = 9.8, never g = 10 and never g = 9.81 — printed on the front of the question paper itself. Source: codex-formula-and-method-bank.md §1.1

FC-002 — Front: How should final numerical answers be rounded, and what rounding errors are penalised? Back: Round to 2 or 3 significant figures. Using g = 9.81 is penalised once per complete question; over- or under-accuracy is penalised once per complete question; premature rounding mid-working is penalised every single time it happens, even more than once within the same question. Source: codex-formula-and-method-bank.md §1.1

FC-003 — Front: What must a "show that" question built on an exact fraction (e.g. sin α = 3/5) do with that fraction throughout the working? Back: Carry it through in its exact fractional form — a decimal substitution anywhere in the chain, even one that rounds correctly, breaks the given-answer mark (verified directly in the June 2025 mark scheme). Source: codex-formula-and-method-bank.md §1.1

FC-004 — Front: Are missing or wrong units (e.g. a missing "N" or "m s⁻¹") usually penalised as an accuracy error on this paper? Back: Not usually — write them anyway as habit, but it isn't usually worth agonising over a missing unit. Source: codex-formula-and-method-bank.md §1.1

FC-005 — Front: What does the entire Mechanics M1 section of the real exam formula booklet actually contain? Back: Nothing M1-specific: it states there are no formulae given for M1 beyond what candidates are expected to know, and that M1 candidates may also need the Pure Mathematics P1/P2 formulae. Every M1-specific relationship has to come from memory. Source: codex-formula-and-method-bank.md §1.0

FC-006 — Front: Which one M1-related formula is genuinely printed in the exam formula booklet (via the P1/P2 extension), and how is it confirmed as a live M1 technique? Back: The cosine rule, a² = b² + c² − 2bc cos A — confirmed as a live technique because Jun 2024 Q2's examiner report discusses candidates using it on a resultant-of-two-forces question. Source: codex-formula-and-method-bank.md §1.0

FC-007 — Front: Which three formula groups does the spec's own text explicitly name as things that must be memorised? Back: Momentum = mv, Impulse = mv − mu, and the five constant-acceleration (suvat) equations. Source: codex-formula-and-method-bank.md §1.0

Section 1 — Mathematical models in mechanics (spec 1.1)

1a. The twelve modelling terms

FC-008 — Front: Particle Back: No size, no shape — all forces act at a single point, no rotation to consider. Source: codex-formula-and-method-bank.md §1.2

FC-009 — Front: Lamina Back: A flat, 2D shape with mass but negligible thickness. Source: codex-formula-and-method-bank.md §1.2

FC-010 — Front: Rigid body Back: Doesn't deform or bend under load. Source: codex-formula-and-method-bank.md §1.2

FC-011 — Front: Light (rod/string) Back: Zero mass — contributes no weight term to any equation. Source: codex-formula-and-method-bank.md §1.2

FC-012 — Front: Uniform (rod) Back: Weight acts at the exact geometric centre. Source: codex-formula-and-method-bank.md §1.2

FC-013 — Front: Non-uniform (rod) Back: Weight acts at a stated, not necessarily central, point — must be given or found. Source: codex-formula-and-method-bank.md §1.2

FC-014 — Front: Inextensible (string) Back: Doesn't stretch — both ends move with identical speed/acceleration magnitude. Source: codex-formula-and-method-bank.md §1.2

FC-015 — Front: Smooth (surface/pulley) Back: Zero friction — no F term anywhere at that contact. Source: codex-formula-and-method-bank.md §1.2

FC-016 — Front: Rough (surface) Back: Friction present — F = μR (moving) or F ≤ μR (equilibrium) applies. Source: codex-formula-and-method-bank.md §1.2

FC-017 — Front: Light smooth pulley Back: Same tension throughout the string on both sides of it. Source: codex-formula-and-method-bank.md §1.2

FC-018 — Front: Bead / wire Back: A particle threaded on a fixed curve/line, constrained to move along it. Source: codex-formula-and-method-bank.md §1.2

FC-019 — Front: Peg Back: A fixed point a string can pass over or hang from, treated as smooth unless stated otherwise. Source: codex-formula-and-method-bank.md §1.2

1b. Modelling as an exam topic, and "show that" discipline

FC-020 — Front: How well-evidenced is spec 1.1 as a standalone exam topic in its own right? Back: It never anchors a full question on its own — in the two series mapped question-by-question in full (Jan 2025, Jun 2025), modelling scored 0 of 2 as a standalone topic, only ever riding as a late sub-part on a kinematics or dynamics question already solved. Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §1

FC-021 — Front: Which single vocabulary term has a confirmed real term-specific critique anchor in the archive reviewed? Back: The light rod — Jan 2020 Q2(b): candidates were expected to know that modelling a beam as a rod meant it did not bend; the commonest wrong answers substituted the equilibrium condition for the modelling consequence itself. Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §3

FC-022 — Front: What is the difference between what an ordinary "find" part marks and what a "show that" (answer-given) part marks? Back: A "find" part marks the destination; a "show that" part marks the argument — because the destination is already printed on the page, reaching it proves nothing by itself. Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §2

FC-023 — Front: In Oct 2019 Q6(e), which three critiques of the model were credited, and which three were rejected? Back: Credited: no instantaneous jump between motion phases, reaction time at the start, stopwatch error at the end. Rejected: air resistance, friction at the ground, the athlete's height/size. Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §5

FC-024 — Front: How does the real mark scheme cap credit on a "name the modelling limitations" question? Back: It caps credit at two named ways and deducts one mark per incorrect extra beyond that count — rewarding precision, not elaboration. Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §5

FC-025 — Front: "Show that" target type 1 — plain numeric target reached by cross-part substitution. What does this shape look like, and where is it confirmed? Back: A value found in an earlier part is substituted into a further equation to reach the part's own printed numeric target — coded a plain M1 (a fresh substitution), not a dependent DM1. Confirmed: Oct 2019 Q6(c). Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §4.1

FC-026 — Front: "Show that" target type 2 — special/boundary-value target. What does this shape look like, and where is it confirmed? Back: A degenerate value (e.g. "show that F = 0") rather than a generic number, testing whether a candidate can tell equilibrium-without-friction apart from limiting friction. Confirmed: Oct 2022 Q3(a). Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §4.2

FC-027 — Front: "Show that" target type 3 — inequality/relational target on an unknown parameter. What does this shape look like, and where is it confirmed? Back: A bound on an unknown, e.g. "hence show that m₂ > ¾m₁" — M1 for the correct sign-inequality on a found velocity, A1★ for the given-answer algebra. Confirmed: Jan 2020 Q1(c). Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §4.3

FC-028 — Front: "Show that" target type 4 — exact-fraction-precision target. What does this shape look like, and where is it confirmed? Back: The final given-answer mark can only be earned from working carried through in the exact fractional form of sin α / cos α — a decimal substitution anywhere in the chain breaks the mark even if it rounds to the right-looking answer. Confirmed: Jun 2025 Q6 (and, per a separate FORGE citation, Jan 2025 Q6 as a second "show that a limiting-angle result" question in the same sub-topic). Source: codex-deep-dive-modelling-assumptions-and-show-that-discipline.md §4.4

Section 2 — Vectors, resultant forces, and bearings (spec 2.1–2.2)

FC-029 — Front: Formula for resolving a force F into components along and perpendicular to a stated reference direction at angle θ. Back: Component along the reference direction = F cos θ; component perpendicular to it = F sin θ. Every resolved term must actually carry a sin or cos factor. Source: codex-formula-and-method-bank.md §1.3

FC-030 — Front: Formula for the magnitude of a vector xi + yj. Back: |v| = √(x² + y²) — Pythagoras, assumed general mathematics, not a booklet entry. Source: codex-formula-and-method-bank.md §1.3

FC-031 — Front: For a force/vector of magnitude F on bearing θ, what are its East (i) and North (j) components? Back: East (i) component = F sin θ; North (j) component = F cos θ — sin goes with the i-component here, the reverse of the "angle-from-the-x-axis" convention most students default to. Source: codex-formula-and-method-bank.md §1.3

FC-032 — Front: What real examiner-report finding confirms the bearing sin/cos-swap trap? Back: Jun 2024 Q7: "a significant number showed a lack of knowledge of bearings," producing the wrong-swapped answer. Source: codex-formula-and-method-bank.md §1.3; codex-deep-dive-resultant-forces-and-bearings.md §3

FC-033 — Front: Formula for the resultant of two forces P and Q, with angle θ between their lines of action (the parallelogram law). Back: R² = P² + Q² + 2PQ cos θ. Source: codex-formula-and-method-bank.md §1.3

FC-034 — Front: What is the confirmed real trap when using the triangle-of-forces/cosine-rule route on a resultant-of-two-forces question? Back: Substituting the wrong one of two angles into the cosine-rule formula — the angle between the forces themselves, or the triangle's own interior angle (its supplement) — even when the triangle itself is drawn correctly (Jun 2024 Q2). Source: codex-formula-and-method-bank.md §1.3; §2.1

FC-035 — Front: State Lami's theorem for three concurrent coplanar forces P, Q, R in equilibrium. Back: P/sin α = Q/sin β = R/sin γ, where each angle is the one between the other two forces, and the three angles sum to 360°. Source: codex-formula-and-method-bank.md §1.3; codex-deep-dive-resultant-forces-and-bearings.md §2.3

FC-036 — Front: Is Lami's theorem printed in the exam formula booklet? Back: No — it is named nowhere in the spec's own text and there is no evidence it is a booklet entry at all; it is confirmed only as a real, examiner-accepted alternative method (Jan 2022 Q1, Jan 2023 Q6). Source: codex-formula-and-method-bank.md §1.3; Genuine gaps flagged

FC-037 — Front: How do you find the resultant of several forces at once (more than two)? Back: Sum every i-component, sum every j-component separately, then take the magnitude/direction of the combined (ΣFx)i + (ΣFy)j — the direct generalisation of the two-force case, which scales to any number of forces without a triangle. Source: codex-formula-and-method-bank.md §1.3; codex-deep-dive-resultant-forces-and-bearings.md §2.4

FC-038 — Front: What real question confirms the three-or-more-force resultant method as literally examined, and what does its resultant sum to? Back: Jan 2025 Q1(a): three named forces summed, per the real mark scheme, to −12i + 18j N. Source: codex-deep-dive-resultant-forces-and-bearings.md §2.4

FC-039 — Front: Formula for the position vector of a particle moving with constant velocity. Back: r(t) = r₀ + t v, where r₀ is the position vector at t = 0 and v the constant velocity vector. Source: codex-formula-and-method-bank.md §1.3

FC-040 — Front: Is two-dimensional projectile motion under gravity part of WME01's spec content? Back: No — spec 3.1's kinematics content is restricted to "motion in a straight line," and every real vector-kinematics question verified for this course uses constant-velocity position vectors, never a 2-D suvat combination with gravity acting in a different direction; that content sits on Pearson's M2 unit. Source: codex-formula-and-method-bank.md §1.3; Genuine gaps flagged

FC-041 — Front: When a question asks for the distance from a moving particle to a fixed point A, what must be computed? Back: r(t) − A first, then the magnitude of that difference — never the magnitude of r(t) alone (a confirmed real trap: computing distance from the origin instead of the stated point). Source: codex-formula-and-method-bank.md §2.3

FC-042 — Front: How do you find the minimum separation between two moving particles, and what real errors are confirmed on this technique? Back: Build the relative position vector AB(t), differentiate |AB(t)|², and set the derivative to zero. Confirmed real errors (Jun 2024 Q7): confusing the t-value at which the minimum occurs with the minimum value itself, and, via an "equal-components" alternative method, an incorrect time value. Source: codex-deep-dive-resultant-forces-and-bearings.md §2.7

Section 3 — Kinematics of a particle moving in a straight line (spec 3.1)

3a. The five suvat equations

FC-043 — Front: Which suvat equation is used when s (displacement) is not needed? Back: v = u + at Source: codex-formula-and-method-bank.md §1.4

FC-044 — Front: Which suvat equation is used when v (final velocity) is not needed? Back: s = ut + ½at² Source: codex-formula-and-method-bank.md §1.4

FC-045 — Front: Which suvat equation is used when u (initial velocity) is not needed? Back: s = vt − ½at² Source: codex-formula-and-method-bank.md §1.4

FC-046 — Front: Which suvat equation is used when t (time) is not needed? Back: v² = u² + 2as Source: codex-formula-and-method-bank.md §1.4

FC-047 — Front: Which suvat equation is used when a (acceleration) is not needed? Back: s = ½(u + v)t Source: codex-formula-and-method-bank.md §1.4

FC-048 — Front: How do you choose which of the five suvat equations to use? Back: List the five quantities (s, u, v, a, t), mark the three given and the one asked for; the equation that doesn't need the fifth (unlisted) quantity is the one to use. Source: codex-formula-and-method-bank.md §2.4

3b. The velocity–time graph

FC-049 — Front: On a velocity-time graph, what does the gradient represent, and which suvat equation does that give directly? Back: The gradient is the acceleration, a = (v − u)/t, which rearranges directly to v = u + at. Source: codex-formula-and-method-bank.md §1.4

FC-050 — Front: On a velocity-time graph, what does the area under the graph represent? Back: The displacement — a trapezium with parallel sides u and v and height t has area ½(u+v)t, exactly the fifth suvat equation, reached with no algebra at all. Source: codex-formula-and-method-bank.md §1.4

FC-051 — Front: What real, confirmed rule governs where a velocity-time graph's shape must start? Back: It must start where the object's own motion actually starts, not automatically at the origin (a real B-mark condition, confirmed in both 2025 series); a continuous line must never be drawn where the real motion has a corner or a gap. Source: codex-formula-and-method-bank.md §1.4

FC-052 — Front: On a displacement-time graph, does the join between two motion stages show a visible "corner" the way a velocity-time graph does? Back: No — s(t)'s gradient is v(t), which is continuous at the join between stages, so the two parabolic arcs join with a continuously turning tangent; only the curvature (a(t)) changes abruptly. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §4

FC-053 — Front: What does an acceleration-time graph show at the join between two motion stages? Back: A vertical jump from height a₁ to height a₂ — the most literal picture of what "two-stage" motion actually means, with nothing to solve on this graph. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §4

FC-054 — Front: When do the speed-time and velocity-time graphs of the same journey diverge from each other? Back: Only if a stage's deceleration continues past v = 0 into reversed motion — for any journey where v(t) never crosses zero, the two graphs are identical. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §4

3c. Two-stage motion

FC-055 — Front: What genuinely forces a two-stage kinematics split, and what does NOT force it? Back: A change in the value of acceleration forces the split — not a reversal of velocity's sign. A particle thrown up under gravity alone (one constant acceleration, −g, the whole flight) is not two-stage. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §1

FC-056 — Front: What is the dominant, most-confirmed trap on two-stage motion questions, and where is it confirmed? Back: Running one suvat equation across both stages instead of resolving each stage independently — confirmed Jan 2023 Q5 (candidates "tried to use t=14 in a single suvat equation," no credit) and Jun 2024 Q5 (candidates "failed to realise there were two distinct stages of the motion"). Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §5.1

FC-057 — Front: In a two-stage motion problem, what is stage 2's own value of u? Back: Stage 1's own final v — not 0, and not any other value — because velocity is continuous at the join between stages. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §3

FC-058 — Front: Does a stage's natural stopping point (where v = 0) always coincide with the stem's own stated boundary? Back: No — a stage can be cut short by a stated distance or time boundary while the particle is still moving. Confirmed: Jun 2024 Q5(b), a landing speed of 4 m/s, not 0; Jan 2023 Q5(c), a stated time boundary instead of a positional one. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §5.2

FC-059 — Front: What real trap involves two particles under the same constant-acceleration model but with offset start times? Back: Jan 2020 Q3 — candidates "wrote down two correct expressions for the displacements" but mismatched the two particles' own starting times when comparing them; the later-starting particle's displacement must be evaluated at τ = t − Δt, not at t itself. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §5.4

FC-060 — Front: What real trap involves a quadratic root that lies outside a suvat model's own valid time domain? Back: Oct 2019 Q6 — candidates "failed to explain clearly why they were rejecting" the invalid root; a stage's s(t) formula is only a truthful description of the motion within that stage's own domain. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §5.5

FC-061 — Front: What confirmed trap connects a two-stage pulley system to a later free-fall stage once the string goes slack? Back: Jan 2025 Q7 — once one particle lands and the string goes slack, the surviving particle continues under gravity g alone, not the shared pulley acceleration; candidates who "used only one equation for the whole of the motion" made no progress. Source: codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §5.6

Section 4 — Newton's second law, scalar and vector form (spec 4.1)

FC-062 — Front: State Newton's second law in scalar form. Back: F = ma, where F is the resultant force, not any single applied force. Source: codex-formula-and-method-bank.md §1.5

FC-063 — Front: State Newton's second law in vector form and explain how it must actually be solved. Back: F₁ + F₂ + ... = ma, with the resultant and ma equated component-by-component: the i-components give one scalar equation, the j-components give a second, independent scalar equation. Solving only one component and assuming the other "matches" is a confirmed real trap. Source: codex-formula-and-method-bank.md §1.5

FC-064 — Front: What two mathematical mechanisms justify treating a vector equation of motion component-by-component? Back: Mechanism 1 — scalar multiplication distributes over components: m(aᵢi + aⱼj) = (maᵢ)i + (maⱼ)j. Mechanism 2 — independent directions force independent equations: c₁i + c₂j = 0 forces c₁ = 0 and c₂ = 0 separately, which is what "equating coefficients" actually is. Source: codex-deep-dive-newtons-second-law-in-vector-form.md §2

FC-065 — Front: What real trap involves a fully correct vector-form N2L method that stops one step short of the answer? Back: Leaving the final answer "as a vector instead of finding the magnitude" when the question asked for a magnitude or a speed — confirmed as the most common error on Jan 2025 Q1(a). Source: codex-deep-dive-newtons-second-law-in-vector-form.md §3.C

FC-066 — Front: What real trap involves adding a force into a vector resultant that was never actually part of the stated system? Back: Adding an unstated weight component (e.g. 2.5g) into a resultant-force calculation for a particle confined to a smooth horizontal plane, where weight and normal reaction cancel exactly and neither has any component inside the i/j plane at all (Jan 2025 Q1(a)). Source: codex-deep-dive-newtons-second-law-in-vector-form.md §3.D

FC-067 — Front: If a question says a resultant force acts "in a direction parallel to" a stated vector, what must you do — and what does the real mark scheme require? Back: Recognise that a stated direction fixes only a ratio of components, not an exact value; the real mark scheme requires a ratio equation in the unknown alone (via λ-elimination if λ is introduced). The confirmed real trap is simply equating the resultant to the direction vector outright (Jan 2025 Q1(b), which resolves to p = −30). Source: codex-deep-dive-newtons-second-law-in-vector-form.md §3.E

FC-068 — Front: What real trap involves both unknowns appearing in both component equations at once (a "cross-wired" system)? Back: Jan 2022 Q6(a): the equations p + 2q = 2 and q + p = −2 give both unknowns in both equations, so equating coefficients alone does not finish the question — the pair has to be solved simultaneously. Source: codex-deep-dive-newtons-second-law-in-vector-form.md §3.B

Section 5 — Connected particles, pulleys, pegs, and lifts (spec 4.2)

FC-069 — Front: What three problem shapes does spec 4.2 actually cover? Back: (i) two connected particles moving in a straight line or under gravity with constant forces, possibly via a smooth fixed pulley or peg; (ii) motion under a force that changes value, the spec's own example being "a particle hitting the ground"; (iii) motion directly up or down a smooth or rough inclined plane. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §1

FC-070 — Front: What mechanism gives every particle on the same string/rod the same magnitude of acceleration? Back: Inextensibility — a string or rod that cannot stretch or compress forces every particle attached to it to travel the same distance, in the same time, as every other particle on the same connector; each particle's own direction of motion is taken as that particle's own positive direction. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §2.1

FC-071 — Front: What mechanism gives a light string one single tension throughout its own length? Back: Masslessness — applying F = ma to the connector itself (mass zero) forces the net force on it to be zero regardless of acceleration, so the pull at both ends of the string is numerically equal. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §2.2

FC-072 — Front: What is the key difference between a string and a rigid rod as a connector? Back: A string can only pull (tension, never thrust); a rigid rod can push or pull, so its internal force can be a tension (positive) or a thrust (negative). Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §1; §2.2

FC-073 — Front: What must every equation of motion in a connected-particles system contain to be dimensionally correct, and what real error results when it's missing? Back: Every term must be a genuine force, and the right-hand side must be that particle's own mass times the shared acceleration — never omit the ma/Ma term. The equation "T − 5g = 9g − T" contains only forces and no acceleration term at all, so it describes equilibrium, not the accelerating system it claims to. Source: codex-formula-and-method-bank.md §2.8

FC-074 — Front: What happens to a connected system when one particle's motion is interrupted (e.g. it lands) and the string running to the other particle goes slack? Back: The surviving particle becomes a free particle under gravity alone (acceleration g, not the shared system value) from that instant, needing a fresh suvat treatment starting from the velocity it had at the exact moment the connector went slack. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §2.3

FC-075 — Front: State the general whole-system shortcut formula for the shared acceleration of a chain of n connected particles. Back: a = (f₁ + f₂ + ... + fₙ)/(m₁ + m₂ + ... + mₙ), where each fᵢ is taken positive in that particle's own direction of motion — valid regardless of how many strings, pulleys, or friction terms sit between the particles, because internal tensions cancel in pairs. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §3.8

FC-076 — Front: Why can the whole-system shortcut never be used to find an internal tension, thrust, or reaction force? Back: Because internal connector forces are exactly the quantities that were summed to zero to get the shortcut in the first place — recovering any one of them always requires falling back to at least one single-particle equation. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §4

FC-077 — Front: In a lift, when does an occupant feel heavier than their own weight, and when do they feel lighter? Back: Heavier whenever the lift's net acceleration is upward — rising and speeding up, or falling and slowing down. Lighter whenever the net acceleration is downward — rising and slowing down, or falling and speeding up. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §3.6

FC-078 — Front: What two separate, real lift-question errors are confirmed across two different series? Back: Jan 2023 Q7: using the mass of the lift alone instead of the whole-system mass. Oct 2022 Q4: the lift's own equation omitted the reactions from the two occupants. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §3.6

FC-079 — Front: What is the most efficient method order for a car-and-trailer (rigid tow-bar) problem, and what real trap is confirmed on its incline version? Back: Write the equation of motion for the simpler particle (the trailer) first, then use its acceleration in the car's own equation — isolate the simpler particle first (Oct 2019 Q3). The confirmed trap on the incline version: "omission of the weight components," an error that can cancel between the two equations and still produce a plausible but uncredited answer. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §3.5

FC-080 — Front: In a two-particles-in-series problem with two separate tensions, what real trap and real requirement are confirmed? Back: Jun 2024 Q3 — "many seemed unfamiliar with this type of situation involving two tensions," specifically missing the mg term for the middle particle's own equation. Both Jun 2024 and Jan 2022 Q7 require the solved tension expressed as a multiple of mg, not as a decimal. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §3.1

FC-081 — Front: Has a bare two-particle pulley system — no incline, friction, or lift attached — been confirmed as a real tested WME01 configuration? Back: No — it is the foundational mechanism every other pulley sub-case builds on, and spec-guidance vocabulary names it, but no named series in the 17 reviewed for this course cites a real WME01 question of precisely this bare shape. Source: codex-deep-dive-connected-particles-pulleys-and-lifts.md §3.2

Section 6 — Momentum, impulse, and conservation of momentum (spec 4.3)

FC-082 — Front: Formula for momentum. Back: momentum = mv Source: codex-formula-and-method-bank.md §1.5

FC-083 — Front: Formula for impulse. Back: impulse = mv − mu — the change in momentum a force produces, where u is the velocity immediately before and v immediately after. Source: codex-formula-and-method-bank.md §1.5

FC-084 — Front: Formula for conservation of momentum in a direct collision between two particles. Back: m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂ — total momentum before equals total momentum after. Every velocity in this equation is signed. Source: codex-formula-and-method-bank.md §1.5

FC-085 — Front: What is the single strongest, most cross-series-confirmed trap in the whole WME01 archive, and in which series is it confirmed? Back: Reporting a signed velocity where the question's own wording asked for an unsigned speed — confirmed independently across three series: Jan 2020, Oct 2022, and Jun 2024. Source: codex-formula-and-method-bank.md §1.5; codex-deep-dive-momentum-impulse-sign-convention.md §7

FC-086 — Front: Why must a WME01 collision question always give you at least one post-collision velocity directly, or specify coalescence? Back: Conservation of momentum is exactly one scalar equation, while the two post-collision velocities are two unknowns. WME01 explicitly withholds Newton's law of restitution (the usual second equation), so the missing second equation must be closed either by given data or by coalescence, which collapses the two unknowns into one by definition. Source: codex-deep-dive-momentum-impulse-sign-convention.md §2

FC-087 — Front: Formula for the combined velocity of two particles that coalesce in a collision. Back: v = (m₁u₁ + m₂u₂)/(m₁ + m₂) — the two post-collision unknowns collapse to one by definition. Source: codex-deep-dive-momentum-impulse-sign-convention.md §4

FC-088 — Front: What real mark-scheme technique turns a signed-velocity requirement into an inequality on an unknown mass? Back: Jan 2020 Q1(c): form the conservation-of-momentum expression for the unknown velocity, then impose the required sign on it (e.g. requiring a rebound, v < 0) to derive an inequality — the real mark-scheme answer is m₂ > ¾m₁. Source: codex-deep-dive-momentum-impulse-sign-convention.md §5

FC-089 — Front: Is the "always strip the sign for a speed" rule absolute across the whole WME01 paper? Back: No — on a different spec point (Jan 2025 Q5(a), vectors, not momentum), asking for a signed velocity, the mark scheme applied no penalty when candidates instead reported an unsigned speed. The exact wording of the specific question part decides which format earns the mark, and strictness varies by series and by part. Source: codex-deep-dive-momentum-impulse-sign-convention.md §6

FC-090 — Front: What real efficiency technique is confirmed for choosing which particle to compute an impulse from in a two-particle collision? Back: Compute the impulse via whichever particle has the simpler known velocities (typically the one starting at rest), rather than the harder one plus a Newton's-third-law sign flip — confirmed Jun 2024 Q1. Source: codex-deep-dive-momentum-impulse-sign-convention.md §7

FC-091 — Front: Is Newton's law of restitution required anywhere on WME01? Back: No — spec 4.3's own guidance explicitly states that knowledge of Newton's law of restitution is not required, and problems are confined to those of a one-dimensional nature. Source: codex-deep-dive-momentum-impulse-sign-convention.md §1

Section 7 — Statics of a particle: equilibrium under coplanar forces (spec 5.1–5.2)

FC-092 — Front: What is the equilibrium condition for a particle under coplanar forces? Back: Resolve in two independent directions and set each resultant to zero — ΣFₓ = 0 and ΣF_y = 0. Every force actually present in the system must appear in at least one of the two equations. Source: codex-formula-and-method-bank.md §1.6

FC-093 — Front: Formula for weight. Back: W = mg — a force, in newtons, not to be confused with mass in kilograms. Source: codex-formula-and-method-bank.md §1.6

FC-094 — Front: What is the confirmed real weight-mass confusion trap? Back: Candidates writing "5g" where the question already supplied a force of 5 N directly — verified in Jan 2022 Q1's examiner report. Source: codex-formula-and-method-bank.md §1.6; codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md §4

FC-095 — Front: What real mark-scheme wording confirms the "incomplete resolution" trap for equilibrium questions? Back: "Incomplete resolutions e.g. 5 = Fcos30 rather than 5 = Fcos30 + Tcos60" (Jan 2022, Q1) — an equation missing a term is a different, wrong equation, marked as a method failure (M0), not an accuracy slip. Source: codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md §2

FC-096 — Front: What four non-friction force types does spec 5.2 name for particle-equilibrium problems? Back: Weight (acts vertically down, mg), normal reaction (perpendicular to a contact surface, away from it, can only push), tension (pulls a taut string toward its anchor, can only pull), and thrust (the same mechanism as tension but for a rigid rod — can push or pull). Source: codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md §1

FC-097 — Front: What three methods are confirmed as fully creditable for a three-force coplanar equilibrium problem? Back: Resolving horizontally and vertically; resolving along/perpendicular to one of the unknown forces; and Lami's theorem or an equivalent triangle-of-forces/sine-and-cosine-rule approach — Jan 2022 Q1 names all three, and Jan 2023 Q6 independently reconfirms the triangle-of-forces/Lami's alternative. Source: codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md §3

FC-098 — Front: Does choosing a faster method (e.g. Lami's theorem instead of resolving) on a three-force equilibrium question earn extra marks? Back: No — the real mark scheme gives a single combined M1/A1 line covering all three credited routes; the only real cost of the slower resolve-and-eliminate route is time, not marks. Source: codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md §3

FC-099 — Front: In Jan 2022 Q1, what extra condition applies to the M1 mark if a candidate resolves horizontally and vertically instead of using a direct method? Back: They must eliminate the second unknown (T) to obtain that mark — the two-unknown horizontal equation alone, with no elimination step, does not itself earn it. Source: codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md §4

Section 8 — Friction: equilibrium, limiting equilibrium, and motion on a rough plane (spec 4.4 / 5.3)

FC-100 — Front: Formula for friction when a particle is moving. Back: F = μR, where R is the normal reaction and μ the coefficient of friction. Source: codex-formula-and-method-bank.md §1.5

FC-101 — Front: Formula/condition for friction in equilibrium or the limiting case. Back: F ≤ μR — friction adjusts up to, but never exceeds, μR, taking the value μR exactly at the point of limiting equilibrium (about to slide). Below that, F is whatever value resolving requires. Source: codex-formula-and-method-bank.md §1.6

FC-102 — Front: How is the direction of friction decided in any problem? Back: Friction opposes actual sliding (moving case) or the tendency to slide (equilibrium case) — never an applied force's own direction. Getting this backwards is the single most cross-series-confirmed error on this whole topic, named directly against Oct 2022 Q3. Source: codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md §2

FC-103 — Front: What real trap is confirmed for a "does it remain at rest?" friction question, and what must the answer actually contain? Back: Jan 2025 Q6(c) — candidates who wrote an "essay" with no calculations scored nothing. Whether an object moves must be decided by an explicit numeric comparison between the driving force and the maximum available friction, never by prose alone. Source: codex-formula-and-method-bank.md §2.11; codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md §3.8

FC-104 — Front: What real, credited method finds μ from a limiting-equilibrium incline scenario under gravity alone? Back: Resolve parallel and perpendicular to the plane, then divide the two resolved equations to eliminate R and solve for μ = tan θ — confirmed Jan 2022 Q5, described as "resolving parallel/perpendicular, eliminating R to solve for μ." Source: codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md §3.2

FC-105 — Front: What real trap involves a string tension given symbolically (e.g. 0.75mg) that also contributes to the normal reaction R? Back: Some candidates "used 0.75 instead of 0.75mg" for the tension, or dropped the string's own perpendicular contribution to R entirely, reaching the incorrect R = mg cos α instead of the correct value that also subtracts the tension's perpendicular component (Jan 2025 Q6). Source: codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md §3.6

FC-106 — Front: What real trap involves a force condition changing mid-question on a rough horizontal plane? Back: Jun 2024 Q6 — removing a rope's vertical tension component changes the normal reaction and therefore the friction and deceleration; candidates "did not recognise that the system was subject to a different acceleration." Source: codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md §3.7

FC-107 — Front: When finding R on an inclined-plane friction question, what must you resolve first and what must you include? Back: Resolve perpendicular to the surface first, including every force with a perpendicular component — not just weight; a string tension or an applied force at an angle to the plane also contributes to R if it isn't parallel to the plane. Source: codex-formula-and-method-bank.md §2.11

Section 9 — Moments: rods on two pivots (spec 6.1)

FC-108 — Front: Formula for the moment of a force about a point. Back: moment = force × perpendicular distance from that point to the force's own line of action. If a force acts exactly at that point, its moment there is zero regardless of the force's own magnitude. Source: codex-formula-and-method-bank.md §1.7

FC-109 — Front: What is the equilibrium condition for a rigid body under coplanar parallel forces? Back: Sum of clockwise moments about any point = sum of anticlockwise moments about that same point (net moment = 0), together with ΣF = 0 in the direction the forces act. Source: codex-formula-and-method-bank.md §1.7

FC-110 — Front: What is the efficient, most-credited method for a moments question with two unknown reactions? Back: One moments equation about either support (eliminating that support's own reaction) plus one vertical-resolve equation — confirmed as the efficient route across three independent series: Jan 2023, Jun 2024, Oct 2023. Source: codex-formula-and-method-bank.md §1.7

FC-111 — Front: What is the one confirmed exception where a single moments equation is NOT enough to solve a rod-on-two-supports problem? Back: If the rod's own weight or centre-of-mass position is also unknown (not just the reactions) — a single moments equation cannot separate two unknowns from one line, and a second, genuinely independent moments equation about the other support is required (Jan 2023 Q4). Source: codex-formula-and-method-bank.md §1.7; codex-deep-dive-moments-rods-on-two-pivots.md Case C

FC-112 — Front: For "the rod is about to tilt about support X," which support's reaction goes to zero? Back: The reaction at the OTHER support, not X — "about to tilt about X" names the support that stays in contact. Confirmed verbatim in Jan 2023 Q4 ("one of the reactions had to be zero") and independently in Jun 2024 Q4 ("an equation with M as the only unknown"). Source: codex-deep-dive-moments-rods-on-two-pivots.md Case B

FC-113 — Front: What real trap involves a rod held by two strings/tensions rather than resting on supports? Back: Jan 2020 Q2 — "the misinterpretation of the given information about the tensions," with candidates misreading "20 N more than" as a multiple (20T) or as two equal unknowns, instead of the correct additive relationship T_D = T_C + 20. Source: codex-deep-dive-moments-rods-on-two-pivots.md Case D

FC-114 — Front: What real trap involves a multi-part moments question where the physical scenario changes between parts? Back: Jan 2025 Q4 — unsuccessful candidates took moments about the correct new pivot but kept "the tension at C still 600N or the particle P still attached," carrying a force forward from an earlier part into a scenario where it no longer belonged. Source: codex-deep-dive-moments-rods-on-two-pivots.md Case E

FC-115 — Front: What is spec 6.1's own stated restriction on the kind of force system it covers? Back: "Coplanar parallel forces" — in practice, every force in every real spec-6.1 scenario is vertical; a rod resting against a wall with friction, or pinned at a hinge with both horizontal and vertical reaction components, sits outside this spec point's own stated scope. Source: codex-deep-dive-moments-rods-on-two-pivots.md §3

Section 10 — Real exam anchors worth recalling directly

FC-116 — Front: Which real WME01 series/question is the fully-mined anchor for the "incomplete resolution" equilibrium trap, and what is its own mark structure? Back: January 2022, Question 1 — two separately-scored 3-mark parts (F alone, then T alone), total 6 marks, with no B mark anywhere in the question; every mark is M or A. Source: codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md §4

FC-117 — Front: In Jan 2022 Q1 (weight 5 N, angle 30°), what are the final answers for F and T? Back: F = 5 cos 30° ≈ 4.3 N; T = 5 sin 30° = 2.5 N. Source: codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md §4

FC-118 — Front: In the January 2025 complete paper, Question 7 (connected particles of mass 2m and 3m over a pulley), what is the shared acceleration and the string tension? Back: a = g/5; T = 2mg + 2m(g/5) = 2.4mg. Source: codex-complete-worked-paper.md Question 7(a)

FC-119 — Front: In January 2025 Q4 (a suspended rod held by two ropes), what value of W is shown by taking moments about A? Back: W = 490 N. Source: codex-complete-worked-paper.md Question 4(a)

FC-120 — Front: In January 2025 Q6 (a particle held on an incline by a string of tension 0.75mg, μ = ½), what value of tan α is shown? Back: tan α = 2/5. Source: codex-complete-worked-paper.md Question 6(b)

FC-121 — Front: In January 2025 Q2 (a speed-time graph with two unknown times), what real misreading trap does the examiner report name? Back: Many candidates treated the total time from A to C as if it were T₂ on its own, consistently throughout — this lost the time-axis and labelling marks even where the resulting arithmetic, applied consistently, still earned follow-through credit elsewhere. Source: codex-complete-worked-paper.md Question 2(a)

FC-122 — Front: In January 2025 Q3(b) (a friction/suvat question), what is the dominant real error the examiner report names? Back: Using u = 0 instead of u = 5 in the suvat step — treating the particle as starting from rest at that point rather than continuing from the speed it already had. Source: codex-complete-worked-paper.md Question 3(b)

FC-123 — Front: In January 2025 Q1(a) (three named forces on a smooth horizontal plane), what two real errors does the examiner report name beyond "left as a vector"? Back: Some candidates added an unstated weight component (2.5g) that the "smooth horizontal plane" setup never places there; a separate, purely transcriptional slip saw "a number of candidates misread 18 for 8" at various stages. Source: codex-complete-worked-paper.md Question 1(a)

FC-124 — Front: In January 2025 Q7(a) (connected particles 2m and 3m), what specific dimensionally-broken equation does the examiner report name, and why does it earn no method credit? Back: "T − 2mg = 3mg − T" — built from real, correctly-signed forces, but with no acceleration term anywhere in it; solved, it describes a system in equilibrium, not one actually accelerating, so it cannot earn the M mark regardless of the number it produces. Source: codex-complete-worked-paper.md Question 7(a)

What this document deliberately does not contain

No likelihood percentage, no grade boundary, and no "confirmed in every series without exception" claim appears anywhere above — every frequency or trap claim on a card is the same named-series count already stated in its source CODEX file, never upgraded. Where a source document itself flags a fact as unverified, an inference rather than a direct spec quote, or a genuine gap in the archive (e.g. the sine rule's own booklet status, or the bare two-particle pulley configuration's real-exam status), the matching flashcard above states that same hedge rather than presenting the fact as more settled than its source does.

Sources

Every card above traces to one of: codex-formula-and-method-bank.md, codex-deep-dive-equilibrium-of-a-particle-coplanar-forces.md, codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md, codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md, codex-deep-dive-connected-particles-pulleys-and-lifts.md, codex-deep-dive-modelling-assumptions-and-show-that-discipline.md, codex-deep-dive-moments-rods-on-two-pivots.md, codex-deep-dive-momentum-impulse-sign-convention.md, codex-deep-dive-newtons-second-law-in-vector-form.md, codex-deep-dive-resultant-forces-and-bearings.md, and codex-complete-worked-paper.md, all in content/veridian/technique-hub/wme01/. No other file was consulted and no new primary-source PDF was fetched for this reformatting pass.