Technique Masterclasses

Mechanics 1

Topic Brief: Friction Equilibrium and Motion on a Rough Plane

Provenance: written 2026-09-29. Primary source: research/veridian/WME01-verified-facts.md — read in full and searched specifically for every friction/4.4/5.2/5.3 entry (§1 spec text, §4 topic 4.2/4.4/5, §5 source-archive scope, §6, §9's per-lesson audit entries). Cross-checked against content/veridian/curriculum/wme01/friction-equilibrium-and-motion-on-a-rough-plane.ts (read in full, so this brief does not repeat its worked exemplars), content/veridian/technique-hub/wme01/codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md (read in full — its §3 variant catalogue and §4 synthesis table are the per-variant detail; this brief does a different job, described below), forge-exam-technique-guide.md (read, for the Jan/Jun 2025 mark-position table and §4's Jan 2025 Q6 findings), signal-frequency-and-boundaries.md (read, for its two-series topic-frequency line on 4.4/5.1–5.3), and content/veridian/question-bank/wme01.ts (searched — it holds nothing specific to this topic, confirmed by both this pass and CODEX's own note). No new primary-source PDF was fetched this pass; every figure below already lives in one of those documents. No Pearson textbook was used anywhere in this course's WME01 research.

SIGNAL Topic Master Brief · Friction — Equilibrium and Motion on a Rough Plane

WME01 (Mechanics 1), spec items 4.4 / 5.2 / 5.3

What this document is for, and what it isn't. CODEX's deep-dive already catalogues this topic's distinct variants one by one — ten of them, each with its own citation and, for two, a fresh worked micro-example. This brief does the roll-up CODEX's own §1 explicitly declines to do: one combined answer to "how often has this topic — as a whole — actually shown up, at what mark weight, in what position in the paper, and in what shape," pulled across the full reviewed archive rather than variant by variant. Read CODEX for method; read this for exam pattern.

1. Every real series confirmed testing this topic

Combining every variant CODEX names its own citation for, friction/equilibrium-on-a-rough-plane is confirmed tested in 5 of the 17 series this course has reviewed a genuine primary source for:

That is 5 named series out of 17 with something checked, not 5 of some larger unchecked total — the other 12 series were not specifically mined for friction/4.4/5.3 content by any document this pass read, so their absence here means "not checked," not "absent." Separately, and not the same number: on the two most recent series that this course has fully, question-by-question mark-mapped (Jan 2025, Jun 2025), spec 4.4 and spec 5.1–5.3 were each seen in 2 of those 2 series (signal-frequency-and-boundaries.md §1) — a real but much narrower finding than the 5-of-17 figure above, and the two counts should never be quoted as interchangeable.

2. The real mark-tariff pattern

Three named series carry this topic as its own dedicated question, and all three land in the same narrow band: Oct 2022 Q3 (3 marks for part (a) + 8 for part (b), summing to 11 by direct addition of the two cited part-totals), Jan 2025 Q6 (12 marks), and Jun 2025 Q6 (11 marks) — an 11–12 mark dedicated question in all three cases this course can name a total for. Jan 2022 Q5 and Jun 2024 Q6 are also confirmed dedicated friction questions, but no single mark-scheme total for either survives in this course's own reviewed evidence, so none is invented here. Separately, Jan 2025 Q3 shows the other real shape this topic takes: one ingredient inside a larger 12-mark combined question (suvat + friction + momentum), with no mark-scheme sub-division by spec point — consistent with this course's standing finding that no WME01 mark scheme reviewed splits a question's marks that finely.

3. Where it sits in the paper

In both fully mark-mapped series, the dedicated friction question sits at Q6 — Jan 2025 has 7 questions total, so Q6 is second-to-last; Jun 2025 has 8, so Q6 is third-from-last. Oct 2022's dedicated friction question was Q3 (of 8), and Jan 2022's was Q5 (of 8) — so across the four dedicated-question instances this course can place in a paper, the position ranges Q3–Q6, roughly the middle to two-thirds mark, and never the final question. That is a genuine contrast worth naming directly: signal-topic-brief-connected-particles-pulleys-and-lifts.md §2 confirms the pulley-then-free-motion question is the paper's final, heaviest question in both of the same two fully mapped series (15 and 17 marks) — the two topics that most often anchor a heavy dedicated question in this paper occupy structurally different slots, not the same one.

4. The recurring context/angle types, by count

No angle above reaches this course's own three-series bar for calling it a standing convention; each is reported at its real, named count.

5. If this topic appears — what to expect

Expect it mid-to-late paper, not first and not the final question — the four dedicated instances this course can place all sit at Q3, Q5, or Q6. Expect an 11–12 mark tariff if it is a dedicated question, in the same band across all three series this course can total; expect no separately-quoted tariff if it instead turns up as one ingredient inside a combined suvat/momentum question. Expect an incline more often than not, but do not assume one — a rough horizontal plane has been confirmed at least once. Above all, expect the paper to test whether the equilibrium ceiling (F ≤ μR) and the moving-case equality (F = μR) are understood as one family split by whether the resultant is zero, not as two separate topics — and check, before resolving anything, whether any force besides gravity has its own component contributing to R.

Sources

research/veridian/WME01-verified-facts.md §1, §4 (topics 4.2/4.4/5), §5, §6, §9. content/veridian/technique-hub/wme01/codex-deep-dive-friction-equilibrium-and-motion-on-a-rough-plane.md §3, §4. content/veridian/technique-hub/wme01/forge-exam-technique-guide.md (mark-position table, §4). content/veridian/technique-hub/wme01/signal-frequency-and-boundaries.md §1. content/veridian/technique-hub/wme01/signal-topic-brief-connected-particles-pulleys-and-lifts.md §2 (cross-topic position contrast). content/veridian/curriculum/wme01/friction-equilibrium-and-motion-on-a-rough-plane.ts. content/veridian/question-bank/wme01.ts (confirmed to hold nothing specific to this topic).