Topic Brief: Modelling Assumptions and Show That Discipline

Provenance: written 2026-09-29. Primary source: research/veridian/WME01-verified-facts.md §1 (spec text), §3 (mark-scheme conventions), §4 topic 1 and topic 6, §5 (source-archive scope, 17 series), §7, and §9's audit entry for this exact lesson — searched and re-read for this topic this session. Cross-checked against content/veridian/curriculum/wme01/modelling-assumptions-and-show-that-discipline.ts (read in full, so this brief does not repeat its worked exemplars), content/veridian/technique-hub/wme01/codex-deep-dive-modelling-assumptions-and-show-that-discipline.md (read, for scope only — this brief does a different job, described below), content/veridian/technique-hub/wme01/signal-frequency-and-boundaries.md (read, for its two-series 1.1 frequency row) and content/veridian/technique-hub/wme01/forge-exam-technique-guide.md (read, for two dated 2025 "show that" mark-tariff data points not yet folded into the lesson file's own citation list). No new primary-source PDF was fetched; every figure below already lives in one of those documents. content/veridian/question-bank/wme01.ts has no item on this topic, consistent with §4/§7's finding that it never anchors a standalone question. No Pearson textbook was used anywhere in this course's WME01 research.

#SIGNAL Topic Master Brief · Modelling Assumptions And Show That Discipline

#WME01 (Mechanics 1), spec item 1.1, plus the cross-topic "show that"/"hence show that" command word

What this brief is for. The lesson file already carries the full worked treatment and states its own scope honestly: this is the thinnest standalone topic in the whole unit. This brief does the roll-up job the lesson doesn't — one place that states exactly how many real series confirm each half of the topic, at what mark weight, and adds two dated 2025 data points on the "show that" exactness rule that the lesson's own citation list does not yet carry.

#1. Every real series confirmed testing this topic

The topic bundles two genuinely different things, so they are counted separately.

Modelling-assumption critique / a modelling term's consequence — confirmed in 2 of 17 series checked:

• Oct 2019, Q6 (final part) — a speed-time graph model; the examiner report is explicit that "the model is clearly described in the second paragraph of the question. Hence only modifications to that model received credit." This is the lesson's own sole real anchor for a critique-the-model question type.
• Jan 2020, Q2(b) — a rod-on-two-pivots question where the credited point is that modelling a beam as a rod means it does not bend; the report records candidates confusing this with the equilibrium condition itself ("clockwise moments equal anticlockwise moments").

No other series in the 17-series archive was found testing either sub-case. The two most recently fully mark-mapped series confirm the same absence directly: signal-frequency-and-boundaries.md's spec-by-spec table records modelling (1.1) at 0 of 2 for Jan 2025 and Jun 2025 — the only spec topic that failed to anchor a question in either series, against every other topic scoring 2 of 2.

"Show that" / "hence show that" command-word discipline — a standing instruction, not a spec-1.1-specific question type: Examiner reports repeat some form of the same instruction — "a full explanation, including all steps, is required to earn full marks... the explanation must use one or more of the previous parts of the question" — across at least 5 of the 17 series checked: Jan 2020, Jan 2023, Oct 2022, Jun 2024, Oct 2023. This is a paraphrase pattern the facts bank itself hedges as "some form of," not five separate verbatim per-series quotes, and it is not unique to spec 1.1 — "show that" is a command word that lands on whichever topic a question happens to be built from.

Two further dated data points, not yet in the lesson file's own citations: Jan 2025 Q6 and Jun 2025 Q6 were both friction-on-an-incline questions carrying a "show that" sub-part. June 2025's specifically states that the final given-answer mark can only be earned from a solution using the exact fractions given (cos α = 4/5, sin α = 3/5) — a decimal substituted mid-working, even one that rounds correctly, breaks the chain. That exactness sub-rule is confirmed in 1 of 17 series so far; treat it as a single real data point, not yet a standing convention.

#2. The real mark-tariff pattern

The two strands carry different weight entirely:

• Modelling-critique never has its own mark total to report, because it never anchors a full question — it rides as a late sub-part on a question already tariffed for something else. The one figure this archive supplies is Oct 2019 Q6(e) itself: B1 B1, 2 marks, for naming two valid refinements, with the mark scheme's own note applying −1 for each incorrect extra beyond two.
• "Show that" sits inside a much heavier question when it appears on a friction/incline scenario: Jan 2025 Q6 was worth 12 of 75 marks; Jun 2025 Q6 was worth 11 of 75 marks. Both are whole-question totals shared across several spec points (4.4, 5.2, 5.3), not marks isolated to the "show that" line itself — no source reviewed for this brief isolates that sub-part's own mark count.

#3. The recurring context/angle, by count

• Modelling critique always rides on an already-solved kinematics or dynamics question, asking the candidate to reread the specific model stated in that question's own stem and name a change consistent with it — never a standalone "define/list the assumptions" question. Confirmed shape in both real instances (Oct 2019, Jan 2020), though the two instances differ in kind (a critique-and-name-changes part vs. a named-term's-consequence part), so "always the same angle" cannot be claimed beyond "always rides on another question."
• "Show that" on a friction-and-incline scenario, with an exact-fraction result: 2 of 17 series (Jan 2025, Jun 2025), both the same broad scenario family (limiting friction on an incline). The exact-fraction penalty specifically: 1 of 17 series (Jun 2025 only).

#4. What the archive does not confirm — stated plainly

No named series in the 17 checked tests spec 1.1's own definitional vocabulary (particle, lamina, rigid body, light/uniform/non-uniform rod, inextensible string, smooth/rough surface, pulley, bead, wire, peg) as a direct recall question — every real citation is a late sub-part riding on something else already being solved. The "5 series" figure for the "show that" instruction is the facts bank's own paraphrase count, not five matched verbatim quotes; treat it with that hedge intact. The exact-fraction "show that" penalty has one confirmed series behind it, not a pattern yet.

#5. If this topic appears — what to expect

Do not expect a standalone modelling-assumptions question; in 17 series checked, including both fully mark-mapped 2025 series, none exists. Expect it instead as the final 2–3 marks of a bigger question, asking you to reread the exact model printed in that stem and name a change consistent with it, or to state what a named modelling term specifically rules out — never a generically true real-world statement disconnected from what the stem actually assumed. "Show that"/"hence show that," by contrast, is not rare at all: expect it on some part of some question most series, and expect three concrete things when it lands — full working to the exact printed target, genuine reuse of an earlier part when the word is "hence," and, if the scenario is a friction/incline problem built on a fraction like 3/5 or 4/5, carrying that fraction through exactly rather than a decimal.

#Sources

research/veridian/WME01-verified-facts.md §1, §3, §4 (topics 1 and 6), §5, §7, §9. content/veridian/curriculum/wme01/modelling-assumptions-and-show-that-discipline.ts. content/veridian/technique-hub/wme01/signal-frequency-and-boundaries.md §1. content/veridian/technique-hub/wme01/forge-exam-technique-guide.md §1, §2 (rounding-convention section).