Skill: course-build → write-mcqs → write-explanation, design-check-sequence @ 11cce8f
Topic 9 — Balanced forces — the PP100's nine 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). Nine types for five atoms, at most two per atom alone plus two pair types — seven four-option MCQs (six easy, one medium) and TWO typed items (one medium, one hard; 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/G3T09.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 and arrow lengths, easy-heavy; types 8 and 9 together carry roughly twelve.
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 four options and a why (no per-option feedback in the bank). Tags follow depth of reasoning: easy = one-step recall or one reading of a drawing; medium = the definition run backwards, a judgement between cases, or the term produced; hard = a chain of two atoms, asked as a ONE-WORD cloze (TEXT ENTRY; the 28 Sep rule: one term or one number, never a phrase). No option bundles a verdict with a reason; every stem is a positive question; the one three-sentence stem is the hard item; no item leans on a video; no item figure carries a verdict or a chip that hands over the answer; panels are lettered J K L M; every exemplar is a FRESH instance — no lesson scene, no quiz scene, no quiz stem (review F14, 28 Sep night). Every drawn arrow obeys the topic's conventions: it starts on the object where the force acts, points the way the force acts, and two arrows of the same length mean the same strength.
Coverage — every atom alone and in a pair
| Atom | Alone | In a pair |
|---|---|---|
| FOR3-040 more than one force can act on the same object at the same time | type 1 | 2 (with 041: a still object with two forces) |
| FOR3-041 a still object can have pushes and pulls acting on it | type 2 | 2 (with 040) |
| FOR3-042 two opposite forces are balanced when they are the same strength | types 3, 6, 8 | 9 (with 045) |
| FOR3-043 while the forces on a still object are balanced, it stays still | type 4 | 7 (with 045) |
| FOR3-045 while the forces on a moving object are balanced, it keeps the same speed and direction | type 5 | 7 (with 043); 9 (with 042) |
No row is empty; every atom sits in at least one pair. FOR3-042 carries three types because it is the capstone the other four feed (the sort every prediction rests on).
The nine types
| Type | Item | Atom | Tag | The stem asks… | The four options are… | Exemplar scene |
|---|---|---|---|---|---|---|
| 1 | PP-1 | FOR3-040 | easy | two named children each pull one end of a rope: which is true of the two pulls | both act on the rope at once / only A's / only B's / neither | Amal and Zayn's rope |
| 2 | PP-2 | FOR3-041 (+040) | easy | a still object: which forces act on it | Earth's pull and the support's push / only Earth's pull / only the push / no forces at all | a plant pot on a windowsill |
| 3 | PP-3 | FOR3-042 | easy | four drawings J K L M of two opposite arrows on one towel: in which are the forces balanced | drawing J / K / L / M — one equal pair; three unequal (left longer; right longer; right longer, both short) | two children and a towel |
| 4 | PP-4 | FOR3-043 | easy | a still object with balanced forces: what does it do | four happenings: stays still / starts to slide / falls off / rises | a jar on a kitchen counter |
| 5 | PP-5 | FOR3-045 | easy | a moving object with balanced forces: what does it do | four happenings, one clause each: keeps the same speed / speeds up / slows down / turns | a tram on a straight street |
| 6 | PP-6 | FOR3-042 | easy (retagged from medium, review S2: one lexicon step) | the forces on a bag are balanced: what do you know about the two pulls | same strength / left stronger / right stronger / only one acting | two children, one strap each |
| 7 | PP-7 | FOR3-045 + FOR3-043 | medium | Mabli says balanced means standing still: which object shows she is mistaken | four objects in one frame — three still (a parked car, a book, a vase), one gliding at a steady speed | a sled gliding |
| 8 | PP-8 | FOR3-042 | medium · TEXT ENTRY | two opposite forces of the same strength: type the word for them | typed: balanced (accept: balanced, balanced forces) | — |
| 9 | PP-9 | FOR3-042 + FOR3-045 | hard · TEXT ENTRY (one-word cloze) | a drawn suitcase pulled along the floor, her pull and the floor's drag the same length: "…the suitcase's speed stays the ___" | typed: same / steady (accept list generated beside the grader's fold) | a girl's suitcase |
Order in the file: easy → medium → hard (PP-1 … PP-9). MCQ keys: A D B B D C C (no letter over 30 %); PP-8 and PP-9 are typed.
The exemplars, in full
Type 1 — PP-1 · FOR3-040 · easy
Stem: Amal and Zayn each pull one end of the same rope, toward themselves. Which is true about the two pulls?
- a) Both pulls act on the rope at the same time. ← key
- b) Only Amal's pull acts on the rope.
- c) Only Zayn's pull acts on the rope.
- d) Neither pull acts on the rope.
Why: Amal pulls the rope. / Zayn pulls the rope. / More than one force can act on the same object at the same time. / So both pulls act on the rope at the same time.
Type 2 — PP-2 · FOR3-041 · easy
Stem: A plant pot stands still on a windowsill. Which forces act on the pot?
- a) only Earth's pull
- b) only the windowsill's push
- c) no forces at all
- d) Earth's pull and the windowsill's push ← key
Why: A still object can have pushes and pulls acting on it. / Earth pulls the pot down. / The windowsill pushes the pot up. / So two forces act on the pot at the same time.
Type 3 — PP-3 · FOR3-042 · easy · figure pp_four_towels
Figure: four panels J K L M of the same two children each pulling one end of a striped towel, a blue arrow from each end. J: the left arrow longer. K: the two arrows the same length. L: the right arrow longer. M: the right arrow longer, both arrows short.
Stem: Two children each pull one end of a towel. In which drawing are the forces on the towel balanced?
- a) drawing J
- b) drawing K ← key
- c) drawing L
- d) drawing M
Why: Two opposite forces are balanced when they are the same strength, and a longer arrow shows a stronger force. / In J, L and M one arrow is longer than the other. / In K the two arrows are the same length. / So drawing K shows balanced forces.
Type 4 — PP-4 · FOR3-043 · easy
Stem: A jar stands still on a kitchen counter, and the forces on the jar are balanced. What does the jar do?
- a) It starts to slide.
- b) It stays still. ← key
- c) It falls off the counter.
- d) It rises up.
Why: The jar is still. / The forces on it are balanced. / While the forces on a still object are balanced, it stays still. / So the jar stays still.
Type 5 — PP-5 · FOR3-045 · easy
Stem: A tram moves along a straight street at a steady speed, and the forces on it are balanced. What does the tram do while the forces stay balanced?
- a) It speeds up.
- b) It slows down.
- c) It turns.
- d) It keeps the same speed. ← key
Why: The tram is moving. / The forces on it are balanced. / While the forces on a moving object are balanced, it keeps the same speed and the same direction.
Type 6 — PP-6 · FOR3-042 · easy
Stem: Two children each pull one strap of a bag in opposite directions, and the forces on the bag are balanced. What do you know about the two pulls?
- a) The left pull is stronger.
- b) The right pull is stronger.
- c) They are the same strength. ← key
- d) Only one of them is really acting.
Why: Two opposite forces are balanced when they are the same strength. / The forces on the bag are balanced. / So the two pulls are the same strength.
Type 7 — PP-7 · FOR3-045 + FOR3-043 · medium (medium because: a judgement between four cases, three of them the misconception's own examples)
Stem: Mabli says that when the forces on an object are balanced, the object must be standing still. Which object shows that Mabli is mistaken?
- a) a car parked in a driveway
- b) a book lying on a table
- c) a sled gliding at a steady speed ← key
- d) a vase standing on a shelf
Why: Balanced forces leave the motion as it is. / The parked car, the book and the vase are still, so they fit what Mabli says. / The sled is moving, and its forces are balanced because its speed and direction are not changing. / So the gliding sled shows Mabli is mistaken.
Type 8 — PP-8 · FOR3-042 · medium · TEXT ENTRY
Stem: Two opposite forces act on one object, and they are the same strength. Type the word we use for these forces.
Accept: balanced · balanced forces
Why: Two opposite forces are balanced when they are the same strength.
Type 9 — PP-9 · FOR3-042 + FOR3-045 · hard · TEXT ENTRY (one-word cloze) · figure pp_suitcase_equal_typed
Hard because: two steps — read the two arrows as the same length, so the same strength, so balanced; then predict what a moving object does while its forces are balanced — and the word is produced, not picked.
Figure: the girl pulls the suitcase to the right; a blue arrow along the handle from the suitcase's top, labeled her pull; a blue arrow back from the suitcase's back, labeled the floor's drag; the two arrows the same length. No chip says balanced, steady or same.
Stem: A girl pulls a suitcase along the floor. The drawing shows her pull and the floor's drag, the same length. While the arrows stay like this, the suitcase's speed stays the ___.
Accept: same · the same · same. · The same · steady · the steady · steady. · The steady
Why: The two arrows are the same length, so the pull and the drag are the same strength. / Two opposite forces of the same strength are balanced. / While the forces on a moving object are balanced, it keeps the same speed. / So the suitcase's speed stays the same.
Design-move inventory (one line per item, against the lessons' checks, practice and taught scenes)
| Item | Move | Nearest existing move | Fresh because |
|---|---|---|---|
| PP-1 | two named pulls on one rope: which is true of them (four sets) | L01 q10 (rope toy: which forces act) | four parallel options; fresh names (Amal, Zayn); no other rope item names its pullers |
| PP-2 | a still object: which forces act (four sets) | L02 q3 (lamp) | a plant pot on a windowsill — no lesson or quiz uses a windowsill |
| PP-3 | four drawings of two opposite arrows: which pair is balanced | L03 q5 (J / K dogs and a rope toy) | a towel, not a rope; four panels, three kinds of unequal |
| PP-4 | still object, balanced: what does it do (four happenings) | L04 q2 (vase) | a jar on a kitchen counter |
| PP-5 | moving object, balanced: what does it do (four happenings) | L05 q7 (horse and cart) | a tram; every option one clause |
| PP-6 | balanced, so what are the strengths | L03 q9 (rope, two options) | a bag with two straps; the fourth option is the FOR-03 trap |
| PP-7 | claim + which object shows it mistaken | L05 q8 (Kaya, bare yes / no) | the judgement between four objects is new |
| PP-8 | produce the term | L03 q12, PR-12 | bank instance of the typed term |
| PP-9 | read equal arrows on a moving thing, complete the one-word prediction (typed) | L05 q4 (sailboat, three options) | a suitcase on a floor; a cloze, one word |