Skill: course-build → write-mcqs → write-explanation, design-check-sequence @ 11cce8f
Topic 10 — Unbalanced forces — the PP100's eight question types, one exemplar each
What this page is. James approves a bank's question TYPES before the bank is generated (vault: A bank is reviewed as its question types first, one exemplar each, 28 Sep 2026; James: "unlikely that you're going to need more than two question types per atom"). Eight types for three atoms, at most two per atom alone plus the pair types — seven four-option MCQs (the easy and medium bulk) and ONE typed item at the hard end (James, 28 Sep night: "hard questions would be text entry or even numeric entry"); this sheet writes ONE exemplar per type in full, exactly as it sits in content/G3T10.py (PP100, flagged TYPE_SHEET_ONLY). No other bank item exists yet. Once the types stand, about fifty items are generated from them, varying scene, nouns, which arrow is longer and where the push lands, easy-heavy; type 8 carries at most eight.
How to read a type line. Each says what the stem asks, what the four options are (the kind of thing), and gives its exemplar scene. Every MCQ has a why (no per-option feedback in the bank; the engine prints Correct / Not quite). Tags follow depth of reasoning: easy = one-step prediction from a described or drawn pair of forces; medium = the rule run backwards (from the change to the forces), or a pick among four drawings or four pushes where the sibling atoms are the distractors, or the pack's "only while it turns" point; hard = a chain of two atoms asked as TEXT ENTRY. No option bundles a verdict with a reason; every stem is a positive question; no bank stem runs to three sentences; every stem states or draws its own scene (nothing leans on the video); no item asks the student to draw; no item figure carries a verdict, a speed word or a path ahead of the thing; lettered panels are J K L M, outside the option alphabet. Every drawn arrow obeys the topic's conventions: it starts on the object where the force acts, points the way the force acts, two opposite forces sit at one height, and the stronger force's arrow is clearly longer.
Coverage — every atom alone and in a pair
| Atom | Alone | In a pair |
|---|---|---|
| FOR3-044 the stronger force acts the way it is moving: it speeds up | type 1 | 4 (with 046: the distractors are 046's and Topic 9's states); 5 (J and M are the speeding sleds); 6 (a push from behind); 8 (with 046, typed) |
| FOR3-046 the stronger force acts against the way it is moving: it slows down | type 2 | 4; 5 (the key); 6 (a push from the front); 8 (Jasper's sled, refused) |
| FOR3-047 a push from the side, nothing against it: it changes direction | types 3, 7 | 6 (with 044 / 046: the three pushes side by side) |
No row is empty; every atom sits in at least one pair.
The eight types
| Type | Item | Atom | Tag | The stem asks… | The four options are… | Exemplar scene |
|---|---|---|---|---|---|---|
| 1 | PP-1 | FOR3-044 | easy | a described pair: the pull forward is stronger than the drag back — what does the object do | four happenings: speeds up / slows down / keeps the same speed / changes direction (the topic's four happenings; review S3) | Yemi's sled on the snow |
| 2 | PP-2 | FOR3-046 | easy | a DRAWN pair, the back arrow longer — what does the object do | the same four happenings | a dad's stroller on a path |
| 3 | PP-3 | FOR3-047 | easy | a described push from the side on a rolling thing — what does it do | four happenings: a new path / faster on the same path / slower on the same path / keeps rolling the same way | Gwen flicks a rolling marble |
| 4 | PP-4 | FOR3-044 + 046 | medium | an object is speeding up — which sentence describes the two forces on it | four states of the forces: forward stronger / back stronger / the same strength / no force | a go-kart on a track |
| 5 | PP-5 | FOR3-046 + 044 | medium | four drawings J K L M of the same object with two arrows each — which shows the one slowing down | drawing J / K / L / M (forward longer; back longer; equal; a push from behind, forward longer) | four sleds on the snow |
| 6 | PP-6 | FOR3-047 + 044 / 046 | medium | a rolling ball — which of these would send it onto a new path | four cases: a push from behind / from the front / from the side / no push at all | a ball on the grass |
| 7 | PP-7 | FOR3-047 | medium | a car drives straight, round a bend, straight again at the same speed — when are the forces unbalanced | four time spans of one shape: the whole time / only on the straight parts / never / only round the bend | a car on a road with one bend |
| 8 | PP-8 | FOR3-044 + 046 (+ 042 as known) | hard · TEXT ENTRY | FOUR drawings headed by children's names (the names appear only on the drawing), one sled with the forward arrow longer, two with the back arrow longer, one balanced — type the name of the child whose sled is speeding up | typed: the child's name (accept list generated: the name; its possessive with a straight, a curly and no apostrophe; "<name>'s sled" both ways) | Rune's, Maeve's, Percy's and Jasper's sleds |
Order in the file: easy → medium → hard (PP-1 … PP-8: types 1–8 in order). MCQ keys: B D C A B C D (no letter over 35 %); PP-8 is typed.
Changed in the 28 Sep night adjudication (review F4, F7, F8, S3): type 8 redesigned to four named panels with the names only on the drawing and a generated accept list; type 7's key shortened to match the distractors' shape; type 6's stem asks "Which of these"; types 1–3's fourth option is the sibling happening, not "stops".
The exemplars, in full
Type 1 — PP-1 · FOR3-044 · easy
Stem: Yemi's pull forward on his sled is stronger than the snow's drag back. What does the sled do?
- a) It keeps the same speed.
- b) It speeds up. ← key
- c) It slows down.
- d) It changes direction.
Why: Yemi's pull forward is the stronger force. / It acts the way the sled is already moving. / So the sled speeds up.
Easy because: one step — the stronger force is named and its direction is the way the sled moves; the rule gives the happening.
Type 2 — PP-2 · FOR3-046 · easy · figure pp_stroller_two_arrows
Stem: The drawing shows the two forces on a stroller rolling along a path. What does the stroller do?
- a) It speeds up.
- b) It keeps the same speed.
- c) It changes direction.
- d) It slows down. ← key
Figure: a dad pushes a purple stroller to the right; a short red arrow HIS PUSH starts at the handle in his hands, a long blue arrow THE DRAG BACK from the back wheel, lower. No speed word.
Why: The arrow back is longer than the arrow forward. / So the drag back is the stronger force. / It acts against the way the stroller is moving, so the stroller slows down.
Easy because: one reading (which arrow is longer) then the rule.
Type 3 — PP-3 · FOR3-047 · easy
Stem: A marble rolls straight across the floor, and Gwen flicks it from the side. What does the marble do?
- a) It rolls slower along the same path.
- b) It rolls faster along the same path.
- c) It rolls off on a new path. ← key
- d) It keeps rolling the same way.
Why: Gwen's flick pushes the moving marble from the side. / Nothing pushes back against her flick, so the forces are unbalanced. / So the marble changes direction and rolls off on a new path.
Easy because: one step — a push from the side on a moving thing, the rule gives the happening; the four options are the topic's three changes and the balanced case, in parallel form.
Type 4 — PP-4 · FOR3-044 + FOR3-046 · medium
Stem: A go-kart is speeding up along the track. Which sentence describes the two forces on it?
- a) The push forward is stronger than the drag back. ← key
- b) The drag back is stronger than the push forward.
- c) The push forward and the drag back are the same strength.
- d) No force acts on the go-kart.
Why: The go-kart is speeding up, so the forces on it are not balanced. / An object speeds up when the stronger force acts the way it is already moving. / The go-kart moves forward, so the push forward is stronger than the drag back.
Medium because: the rule is run backwards — from the observed change to the state of the forces — and the distractors are the two sibling states (the slowing case, the balanced case) plus the catalogue's "no force on a moving thing" belief.
Type 5 — PP-5 · FOR3-046 + FOR3-044 · medium · figure pp_four_sleds
Stem: Four sleds slide along the snow. Which drawing shows the sled that is slowing down?
- a) drawing J
- b) drawing K ← key
- c) drawing L
- d) drawing M
Figure: four panels J K L M, each a sled on snow moving right with two arrows at two heights (the pull from the rope tie, the drag lower from the runner's end): J forward longer (a girl pulls); K back longer (a girl pulls); L equal (a girl pulls); M a boy pushes from behind, the red forward arrow longer. No speed word, no tick or cross.
Why: A sled slows down when the stronger force acts against the way it is moving. / In J and M the arrow forward is longer: those sleds speed up. In L the arrows are equal: that sled keeps its speed. / In K the arrow back is longer, so the drag back is the stronger force and sled K slows down.
Medium because: four drawings are read and three refused — two speeding (one by a pull, one by a push) and one balanced — before the slowing one is picked.
Type 6 — PP-6 · FOR3-047 + FOR3-044 / 046 · medium
Stem: A ball is rolling along the grass. Which of these would send it onto a new path?
- a) a push from behind
- b) a push from the front
- c) a push from the side ← key
- d) no push at all
Why: A push from behind acts the way the ball is moving and speeds it up; a push from the front acts against it and slows it down. / With no push, the ball keeps rolling the same way. / Only a push from the side changes the ball's direction, so only that push sends it onto a new path.
Medium because: the student holds the three atoms side by side and picks the one push whose direction gives a change of direction; the other two pushes are the speed-change atoms.
Type 7 — PP-7 · FOR3-047 · medium
Stem: A car drives along a straight road, round a bend, and along a straight road again, all at the same speed. When are the forces on the car unbalanced?
- a) the whole time
- b) only on the straight parts
- c) never
- d) only round the bend ← key
Why: Balanced forces leave the motion as it is; unbalanced forces change it. / On the straight parts, at the same speed, nothing about the car's motion changes. / Round the bend its direction changes, so the forces are unbalanced only while it goes round the bend.
Medium because: the pack's L9 point (James: "the forces are unbalanced only while the car is turning… we need to make that clearer") asked as a WHEN — the student separates the turning moment from the straight moments and refuses "the whole time", the natural over-generalisation.
Type 8 — PP-8 · FOR3-044 + FOR3-046 · hard · TEXT ENTRY · figure pp_four_sleds_named
Stem: The drawings show the two forces on four children's sleds. Type the name of the child whose sled is speeding up.
Accept (generated by name_accept("Maeve", "sled"), never hand-typed): Maeve · Maeve's · Maeve’s · Maeves · Maeve's sled · Maeve’s sled (case, articles and a final period are ignored by the grader; no synonym — the answer is a name, and the names appear only on the drawing)
Figure: four panels headed RUNE'S SLED, MAEVE'S SLED, PERCY'S SLED, JASPER'S SLED; in each a child pulls a sled to the right on the snow with two blue arrows, the pull from the rope tie and the drag lower from the runner's end; Rune's arrows are equal, Maeve's forward arrow is the longer, Percy's and Jasper's back arrows are the longer.
Why: A sled speeds up when the stronger force acts the way it is already moving. / On Rune's sled the arrows are equal, so it keeps its speed; on Percy's and Jasper's the arrow back is longer, so they slow down. / On Maeve's sled the arrow forward is longer, so her pull is the stronger force and her sled speeds up.
Hard because: four drawings are read — which arrow is longer and which way it acts — the rule is applied to each (FOR3-044 once, FOR3-046 twice, the balanced case once), three sleds are refused and the answer is produced, not recognised. Typed, per James's ruling that the bank's hard items are text or numeric entry; the generated items of this type vary the four children, the object (sled, wagon, toy train, boat) and which panel carries the longer forward arrow. No numeric type: the topic attaches no number to any arrow. (Review F4: the first draft showed two named sleds and printed both names in the stem — a coin flip; redesigned 28 Sep night.)
Reading notes for the review
- Every type reuses a form the lesson quizzes and the mixed practice already use, with four options (James's Topic 3 night ruling): type 1 is L01's described-pair item; type 2 is L02's drawn-pair item; type 3 is L03's puck item; type 4 is the "which force is stronger" item L01 and L02 run backwards; type 5 widens the drawn pair to four panels; type 6 is L03's "push from behind vs from the side" contrast as one item; type 7 is L03's car-on-the-bend item asked as a when; type 8 is four drawn pairs made a typed chain.
- No item asks anyone to draw. Arrow items are reading items on drawn arrows, and the drawing carries no verdict, speed word, tick, cross or path ahead of the thing; the blind comment says which arrow is longer and stops.
- "You cannot tell" is not offered anywhere: no exemplar has a scene where it would be the honest answer. "The same strength" (type 4), "no push at all" (type 6) and "never" (type 7) are genuine states a student might believe, not padding.
- Scenes are fresh against the lessons (the girl's wagon; the boy's cart, the rug; the boy's bike; the ball on the grass; the kicked ball and the toy boat from above), against the lesson quizzes (a gliding sled, Hiro's sled, Amira's scooter, a boy's toy train, Dalia's boat, Bashir's sled, a skateboard, a toy car, Sven's go-kart, Eloise's sled; Vera's toy duck, a train at a station, Delphine's boat, a toy train, Kenzo's ball, Umar's skateboard, a scooter, Farid's thrown ball, Thandi's ball, Kavya's puck, Rafa's sled; a marble, a hockey puck, a bird, the J / K marbles, Leilani's ball, the car on the bend, the swerving ball, Gideon's car, Imogen's leaf) and against the practice set (Yosef's toy dog, Zola's skateboard, a canoe, Marek's toy train, a toy truck, Wyatt's claim, Oskar's boat, Kaia's scooter). Type 4's go-kart appears once in a quiz as a claim (Sven), a different move. Type 5 and 8 reuse the sled glyph because the sled is the topic's cleanest two-force object on snow; each is a fresh instance (four lettered panels; four named panels) and a different move from the quiz's single sled items.
- Not planned: any multi-select; none of these answers is a set. No verdict-and-reason option anywhere. No numeric-entry type: the topic is qualitative, so text entry is the typed form.
- Names used in this topic: Hiro, Wanda, Dalia, Bashir, Sven, Eloise (L01); Vera, Delphine, Kenzo, Umar, Farid, Thandi, Kavya, Rafa (L02); Leilani, Gideon, Imogen (L03); Yosef, Zola, Marek, Wyatt, Oskar, Jorge (practice); Yemi, Gwen, Rune, Maeve, Percy, Jasper (bank). None appears in any other topic's content file, Topic 9 included (checked by grep over
grade3/topic*_build/content/; Amira and Kaia were renamed after the review found near-collisions with Topic 9's Amara and Kaya).