Mechanics 1
Topic Brief: Kinematics Constant Acceleration Two Stage Motion
Provenance: written 2026-09-29. No new primary-source mining was done for this document — every citation is reused from, and re-checked against, three existing sources: research/veridian/WME01-verified-facts.md §3–§4 topic 3 and §9's lesson-audit entry (the provenance-checked primary-source quotes), codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md §5–§6 (the fullest existing per-series breakdown, re-sorted here rather than restated), and signal-frequency-and-boundaries.md §1 (the paper-wide mark table, read for spec-3.1 values only). The "17 series checked" denominator is WME01-verified-facts.md §5's own count of distinct series with a genuine primary document reviewed for this paper. This document's job: one series-indexed, mark-tariff-aware brief for this single sub-topic — no new fact is introduced.
SIGNAL · WME01 Topic Master Brief — Kinematics: Constant-Acceleration Two-Stage Motion
For the derivations, the worked chain, and the full theoretical treatment, use the lesson file and codex-deep-dive-kinematics-constant-acceleration-two-stage-motion.md. This document does one thing only: for this specific sub-topic, which real series tested it, at what mark tariff, in what recurring shape, and what to expect if it shows up on your paper.
1. Series index
Six distinct series, out of the 17 with a genuine primary document reviewed for WME01, contribute to this topic family. Read the narrow and broad rows separately — they are not the same claim.
| Sub-case | Seen in | Series (question) | Real context |
|---|---|---|---|
| Core trap — one suvat equation run across two genuinely different acceleration phases | 2 of 17 | Jan 2023 (Q5), Jun 2024 (Q5, 14 marks) | A vehicle in two distinct phases (P→Q→R); a falling box that then decelerates under a parachute |
| Second stage cut short by a stated boundary, not run to rest | 2 of 17 | Jun 2024 (Q5, same question, part (b)/(d)); Jan 2023 (Q5, same question, part (c)) | Landing speed scored at the ground, not ; distance asked for at a stated , not at natural stop |
| Connected-particles-then-free-motion hybrid (spec 4.2 combo, same handover discipline) | 2 of 17 | Jan 2025 (Q7, 15 marks, shared with 4.2), Jun 2025 (Q8, 17 marks, shared with 4.2) | A pulley system runs, then one particle continues under gravity alone — owned primarily by the connected-particles lesson, listed here because the trap is identical |
| Three-phase v-t graph, one phase's duration unknown (), solved via total area | 1 of 17 | Jan 2023 (Q1) | Accelerate, cruise, decelerate over a stated total distance |
| Two particles under the same acceleration model, offset start times | 1 of 17 | Jan 2020 (Q3) | One particle released after the other; candidates compared displacements at inconsistent values of |
| Quadratic root outside the motion's valid time domain | 1 of 17 | Oct 2019 (Q6) | A suvat-derived quadratic has two roots; one is not physically reachable |
The core trap and its boundary sub-case are the same two questions (Jan 2023 Q5, Jun 2024 Q5) read for two different parts, not four independent confirmations. As one trap family, "two-stage motion where a single suvat equation silently spans two different accelerations" is confirmed in 2 of the 17 series checked; widened to include the connected-particles hybrid, 4 of 17; widened again to every adjacent angle in the table, 6 of 17.
2. Mark-tariff pattern
Only three of the six series above have a documented total mark value for the anchor question, and this brief states only those three rather than guessing at the rest:
- Jun 2024 Q5 — 14 marks. The single verified mark total for the core trap in its plain (non-hybrid) form.
- Jan 2025 Q7 — 15 marks (shared with spec 4.2). Jun 2025 Q8 — 17 marks (shared with spec 4.2). Both are the connected-particles hybrid, and both are, per
forge-exam-technique-guide.md, the last and heaviest question on their paper — a two-series pattern the FORGE document itself flags as short of the 3+-series bar this course wants before calling something a standing convention.
No mark total for Jan 2023 Q5, Jan 2023 Q1, Jan 2020 Q3, or Oct 2019 Q6 was located in the sources checked — a gap in what has been recorded, not a claim about the topic's importance. What the three known figures do support: every time this topic (plain or hybrid) has a recorded mark total, it has been a substantial, multi-part allocation (14–17 marks), never a short 4–6 mark item. Three data points is not enough to call that a rule for every series, only a real, narrow pattern in what has actually been checked.
3. Recurring context and angle
Two real trigger-shapes account for every core-trap citation above:
- A stated physical event splits the motion — a force added or removed, a surface change, a parachute deploying, a string going slack. Confirmed in Jan 2023 (Q5) and Jun 2024 (Q5), and in the hybrid form in Jan 2025 (Q7) and Jun 2025 (Q8).
- The second stage is cut off by a stated distance or time, not by the particle coming to rest. Confirmed in the same two anchor questions (Jun 2024 Q5's ground boundary; Jan 2023 Q5's stated ).
The three single-series adjacent angles are each a different discipline riding on the same "carry a value across a boundary" skeleton — an unknown time solved from total area (Jan 2023 Q1), an unknown origin for a second clock (Jan 2020 Q3), and an unknown domain for a solved variable (Oct 2019 Q6) — not the same trap as the two-stage core, and not claimed as such.
4. If this topic appears — what to expect
- Expect a multi-part question, not a one-line calculation — every anchor question above has at least four lettered parts.
- Expect the split to be triggered by a named event in the stem (a force change, a surface change, an opened parachute, a slack string) — reread the stem specifically for that event before writing a single suvat equation.
- Expect the examiner to check whether you found the second stage's own natural stopping point () and compared it against any stated distance/time boundary, rather than assuming they coincide.
- If the question also involves a pulley or connected particles, expect this to be the paper's final, heaviest question — true in both series checked for that hybrid (Jan 2025, Jun 2025), not yet confirmed as a rule beyond those two.
- Nothing above is a probability. It is a description of what six named series, out of the 17 with a genuine primary document reviewed for this paper, have actually contained.
Genuine gaps, flagged
- The remaining 11 of 17 series were not searched question-by-question for this specific sub-topic in the sources this brief draws on; a series absent from §1's table has not been checked for this trap, not confirmed clear of it.
- Jan 2025's and Jun 2025's own spec-3.1 questions outside Q7/Q8 (e.g. Jan 2025 Q2/Q3, Jun 2025 Q3) are confirmed to carry real spec-3.1 marks (
signal-frequency-and-boundaries.md§1) but were never deep-mined for this specific trap — not counted in §1's index, and not assumed to test it. - Mark totals for four of the six anchor questions were not found in this course's existing WME01 material; §2 states three figures, not six, rather than filling the rest with an estimate.