Skill: course-build → write-mcqs → write-explanation @ df153ae · v2 (2 Oct 2026, reviews applied): write-mcqs, write-explanation @ b0fa825
Topic 1 — question types in the PP100 bank, one exemplar each (v2)
James (2 Oct 2026): the bank is part of the topic, written with the lessons, no type-sheet gate. This sheet still prints ONE exemplar per question type in
full, as it ships in content/G4T01_pp100_bank.py, so James reads the types first. Item ids are bank positions (PP-1 … PP-50; easy PP-1–18, medium
PP-19–39, hard PP-40–50). Every item carries exactly one atom, a type_ (its row below) and a why; hard items carry a hb ("hard because") line.
v2 renumbered the bank (two items cut): the v1 → v2 map is in BUILD_RECORD_G4T01.md, section "v2 — reviews applied".
Bank: 50 items — 18 easy · 21 medium · 11 hard; 47 four-option MCQs, 3 typed (text), 0 multi-selects. Per atom: FOR4-001 14 (10 easy · 3 medium · 1 hard),
FOR4-002 11 (2 easy · 6 medium · 3 hard), FOR4-003 13 (4 easy · 5 medium · 4 hard), FOR4-005 12 (2 easy · 7 medium · 3 hard) — difficulty rises with the atom's position. Typed: "friction" three
times (FOR4-001, FOR4-002, FOR4-005); the sort labels "helpful" / "unhelpful" are never typed (v2: the guidance review ruled a typed verdict an MCQ in
disguise, and the brake item was the article's own case). Key letters of the 47 MCQs in bank order: A B C D B C B D A B C D C C A D C D A B C A B D C D A A B C C A A B C D A B D B C D D B C A D —
A 11 · B 11 · C 13 · D 12 (max 28 %); no four alike in a row, no ABAB run.
Fresh instances. No bank scene appears in a lesson, its quiz, an attached question or the practice set (v2 re-instanced the four that did: the toy train,
the toy car on a carpet, the two toy cars, Darnell's toy car on the rug). The design-move inventory at the end lists, per item, the move, the scene kind and
the nearest lesson-side instance.
The nine live types (type 10 retired in v2)
| # | Question type | Exemplar | Items (typed starred) | Count | Hard end |
|---|---|---|---|---|---|
| 1 | Where does friction act (or where do two surfaces rub): a described scene; four places, one the rubbing contact, one "nowhere" (true only when the thing touches nothing). | PP-1 | PP-1, PP-2, PP-3, PP-4, PP-7, PP-8, PP-9, PP-10, PP-20 | 9 | none |
| 2 | Name the force: a definition or a rubbing scene; four force words (weight, friction, a pull, speed); hard form — type the name from the definition, the stopping rule, or a chain of scenes. | PP-5 (easy) · PP-40* (hard) | PP-5, PP-21, PP-40, PP-41, PP-49* | 5 | text ("friction") |
| 3 | In which direction does friction push: the sliding direction stated; four directions. | PP-6 | PP-6, PP-19 | 2 | none |
| 4 | What stopped it / what happens next: a thing let go of; four causes, or four outcomes. | PP-11 | PP-11, PP-12, PP-23, PP-24, PP-42 | 5 | MCQ (PP-42: chain) |
| 5 | Why it keeps going / why it stopped: reasons as options; the FOR-01 ("ran out") and FOR-02 ("something must still push it") corrections among them; a claim with the verdict fixed. | PP-22 | PP-22, PP-25, PP-26, PP-27, PP-43 | 5 | MCQ (PP-43: judge a claim) |
| 6 | Which surface: farthest, most friction, sooner, or more friction than a named surface, from four options after the same push; distances as evidence of friction; hard — four distances to order, or four surfaces against a fifth. | PP-13 (easy) · PP-45 (hard) | PP-13, PP-14, PP-15, PP-30, PP-32, PP-45, PP-47 | 7 | MCQ (PP-45: data read + inference; PP-47: the four surfaces are placed against a fifth that is not among the options, with no scene to lean on) |
| 7 | The reason for a distance difference, or a change that would lower friction: FOR-12 ("pushed harder") as a distractor; hard — the FOR-12 claim judged by its reason. | PP-28 | PP-16, PP-28, PP-29, PP-31, PP-44, PP-46 | 6 | MCQ (PP-44: judge a claim's reason; PP-46: apply the rule backwards) |
| 8 | Helpful or unhelpful: four scenes, pick the odd one; who wants more friction. (v2: the sort is never typed — a typed verdict is an MCQ in disguise.) | PP-17 | PP-17, PP-18, PP-36, PP-38 | 4 | none |
| 9 | Why friction helps here (the grip or the slowing wanted), what a change did to the friction, or which change would help where the sliding is wanted; a claim about friction judged by its reason (FOR-08). | PP-33 (medium) · PP-48 (hard) | PP-33, PP-34, PP-35, PP-37, PP-39, PP-48, PP-50 | 7 | MCQ (PP-48: apply the sort backwards; PP-50: judge a claim about an imagined removal) |
| 10 | Select the set (multi-select). Retired in v2: both set items were split into single-answer MCQs (PP-47; the helpful-places set cut), so the bank holds no multi-select. | — | — | 0 | — |
Why typed is the hard end for the term. Picking "friction" from four is recognition; typing it from the definition, from the stopping rule with its term
removed, or across three unlike scenes is production. Where nothing is produced (a direction, a surface, a reason, a verdict), the hard form stays an MCQ that
chains two ideas, reads data or judges a claim's reason, each with its "hard because" line.
How the grader reads a typed answer: lower-case, trim, collapse spaces, drop a final period; it strips neither articles nor plurals, so each accept
list carries "friction", "the friction", "a friction", "frictions", "friction force", "the friction force", "force of friction", "the force of friction" (v2)
and the child spellings the brief asked for (frikshun, fricshun, friciton, fricton, friktion, frition).
The exemplars, printed in full
Type 1 — exemplar PP-1
PP-1 · atom FOR4-001 · easy · type 1
Stem: A dog's water bowl is pushed across the kitchen floor and slides. Where does friction act on the bowl?
- a) where the bowl rubs the floor ← key
- b) between the bowl and the air
- c) inside the bowl, in the water
- d) nowhere
Why: Friction acts where two surfaces rub. / The bowl rubs against the floor as it slides. / So friction acts where the bowl rubs the floor.
Type 2 — exemplar PP-5 (easy) · PP-40 (hard)
PP-5 · atom FOR4-001 · easy · type 2
Stem: Where two surfaces rub, a force pushes against the sliding. What is this force called?
- a) weight
- b) friction ← key
- c) a pull
- d) speed
Why: The force that acts where two surfaces rub, against the sliding, is called friction. / Weight is Earth's pull on a thing. / A pull moves a thing toward the puller. / Speed is how fast a thing moves, not a force.
PP-40* · atom FOR4-001 · hard · type 2 · text
Stem: A toboggan slides down a snowy hill. Where the toboggan rubs the snow, a force pushes against the sliding. Type the name of this force.
Accept: friction · the friction · a friction · frictions · friction force · the friction force · force of friction · the force of friction · frikshun · fricshun · friciton · fricton · friktion · frition
Hard because: production: the term is typed from its definition, nothing to pick from.
Why: The force that acts where two surfaces rub, against the sliding, is called friction. / The toboggan rubs against the snow. / So the force there is friction.
Type 3 — exemplar PP-6
PP-6 · atom FOR4-001 · easy · type 3
Stem: A box slides to the right across a floor. In which direction does friction push on the box?
- a) to the right, with the sliding
- b) straight up, off the floor
- c) to the left, against the sliding ← key
- d) straight down, into the floor
Why: Friction pushes against the sliding. / The box slides to the right. / So friction pushes the box to the left.
Type 4 — exemplar PP-11
PP-11 · atom FOR4-002 · easy · type 4
Stem: Elena taps a golf ball, and it rolls across the putting green, slows down, and stops. What stopped the golf ball?
- a) the ball's weight
- b) the tap running out
- c) friction between the ball and the green ← key
- d) the green pushing the ball forward
Why: A moving thing does not stop by itself. / Where the ball rubs the green, friction pushes against the rolling. / Friction slows the ball a little more every moment, until it stops. / So friction stopped the golf ball.
Type 5 — exemplar PP-22
PP-22 · atom FOR4-002 · medium · type 5
Stem: A curling stone slides across the ice and keeps going a long way before it stops. Why does it go so far?
- a) Only a little friction pushes against it. ← key
- b) The ice pushes it forward.
- c) Its push is still inside it.
- d) No force at all acts on it.
Why: A sliding thing slows down because friction pushes against it. / Ice is smooth, so only a little friction pushes against the stone. / So the stone slows only a little each moment, and it goes a long way before it stops.
Type 6 — exemplar PP-13 (easy) · PP-45 (hard)
PP-13 · atom FOR4-003 · easy · type 6
Stem: Reed slides a coin with the same gentle push across four surfaces. On which surface does the coin slide farthest?
- a) a wool blanket
- b) a gravel path
- c) a glass table top ← key
- d) a doormat
Why: A smoother surface has less friction, so the same thing slides farther on it. / The glass table top is the smoothest of the four. / So the coin slides farthest on the glass.
PP-45 · atom FOR4-003 · hard · type 6
Stem: Elena pushes the same cup the same way across four surfaces. It slides 20 centimeters on a towel, 60 centimeters on cardboard, 150 centimeters on tile, and 400 centimeters on ice. Which surface is the smoothest?
- a) the towel
- b) the cardboard
- c) the tile
- d) the ice ← key
Hard because: data read + inference: the student turns four distances from the same push into an order of friction, then of smoothness.
Why: The push was the same on every surface. / A smoother surface has less friction, so the same push takes the cup farther. / The cup went farthest on the ice, 400 centimeters. / So the ice is the smoothest surface.
Type 7 — exemplar PP-28
PP-28 · atom FOR4-003 · medium · type 7
Stem: After the same push, a sled goes farther on packed snow than on gravel. Which sentence explains why?
- a) The packed snow has less friction than the gravel. ← key
- b) The gravel has less friction than the packed snow.
- c) The packed snow pushes the sled forward.
- d) The sled's push lasts longer on snow.
Why: A smoother surface has less friction, so the same thing slides farther on it. / Packed snow is smoother than gravel, so it has less friction. / So the sled goes farther on the packed snow.
Type 8 — exemplar PP-17
PP-17 · atom FOR4-005 · easy · type 8
Stem: Friction is helpful in three of these. In which one is friction unhelpful?
- a) a horse's hooves gripping the trail
- b) a truck's tires gripping a steep hill
- c) a door that sticks in its frame ← key
- d) a climber's hands gripping a rope
Why: Friction is helpful when you want the grip or the slowing, and unhelpful when you want the sliding. / The hooves, the tires and the hands all want the grip. / You want the door to swing, not stick. / So friction is unhelpful at the sticking door.
Type 9 — exemplar PP-33 (medium) · PP-48 (hard)
PP-33 · atom FOR4-005 · medium · type 9
Stem: Reed sprinkles sand on the icy steps. Why does the sand help people walk on them?
- a) The sand gives the steps more friction. ← key
- b) The sand melts the ice.
- c) The sand makes the steps smoother.
- d) The sand makes the steps warmer.
Why: Friction is helpful when you want the grip. / Sand is rough, so sand on the ice gives the steps more friction. / More friction lets shoes grip the steps. / So the sand helps people walk on them.
PP-48 · atom FOR4-005 · hard · type 9
Stem: The sliding glass door drags and sticks on its track. Which change would help it slide?
- a) oiling the track ← key
- b) sand on the track
- c) a rougher track
- d) pressing the door harder onto the track
Hard because: apply the sort backwards: the sliding is wanted, so the student picks the one change that lowers friction.
Why: Friction is unhelpful when you want the sliding. / You want the door to slide along its track. / Oil makes the track smoother, so there is less friction. / So oiling the track helps the door slide.
Hard items, with their "hard because" lines (bank order)
| Item | Atom | Form | Hard because |
|---|---|---|---|
| PP-40 toboggan | FOR4-001 | text | production: the term is typed from its definition, nothing to pick from |
| PP-41 the stopping rule | FOR4-002 | text | production: the stopping rule is given without its term and the student supplies it |
| PP-42 two balls, doormat and floor | FOR4-002 | MCQ | chain: the student sees one force behind two different distances (more friction on the doormat, less on the floor) |
| PP-43 "nothing was pushing it along" | FOR4-002 | MCQ | judge a claim: the student rejects FOR-02 (it needs a pusher), FOR-01 (the push ran out) and the by-itself story for the taught cause |
| PP-44 "I must have pushed harder" (mat / tiles) | FOR4-003 | MCQ | judge a claim's reason: the student holds the push the same (FOR-12) and reads the longer distance as less friction |
| PP-45 four distances | FOR4-003 | MCQ | data read + inference: the student turns four distances from the same push into an order of friction, then of smoothness |
| PP-46 the plastic sheet (toy robot) | FOR4-003 | MCQ | apply the rule backwards: the student chooses the change that lowers friction, with the same push |
| PP-47 more friction than a wool rug | FOR4-003 | MCQ | the four surfaces are placed against a fifth that is not among the options, with no scene to lean on |
| PP-48 the sliding door's track | FOR4-005 | MCQ | apply the sort backwards: the sliding is wanted, so the student picks the one change that lowers friction |
| PP-49 three places, one force | FOR4-005 | text | chain + production: three unlike scenes, helpful and unhelpful, are seen as one force and it is named |
| PP-50 walking without friction | FOR4-005 | MCQ | judge a claim about an imagined removal: the student reasons from the grip to what walking needs |
Design-move inventory (every bank item: move · scene kind · nearest lesson-side instance)
| Item | d | Atom | Move | Scene kind | Nearest lesson-side instance |
|---|---|---|---|---|---|
| PP-1 | easy | 001 | locate friction on a sliding thing | a bowl pushed across a kitchen floor | L01-q9 book on a desk (same move, new thing and surface) |
| PP-2 | easy | 001 | locate friction | a child on cardboard down a grassy hill | L01-q8 the slide |
| PP-3 | easy | 001 | locate friction | a snowboard on snow | intro sled on snow (the intro teaches nothing; the bank may use its kind) |
| PP-4 | easy | 001 | locate the rubbing pair, the no-rub case (asked as 'where do two surfaces rub?') | an apple falling from a tree, touching nothing | L01-q5 the falling acorn |
| PP-5 | easy | 001 | name the force from the definition | none | L01-q10 backpack on grass |
| PP-6 | easy | 001 | direction of friction | a box sliding right | NEW move (the quizzes never ask the direction) |
| PP-7 | easy | 001 | which of four has nothing rubbing | sled / ball over a net / chair / toboggan | L01-q3 basketball in the air |
| PP-8 | easy | 001 | which two surfaces rub | a shopping basket on a store floor | L01-q4 bench on the hall floor |
| PP-9 | easy | 001 | locate friction | a garden hose dragged across a lawn | L01 video bag on grass |
| PP-10 | easy | 001 | locate friction on a thing that has stopped (v2: retagged FOR4-001 — a locate item) | a pencil on a desk | L01-q9 book on a desk |
| PP-11 | easy | 002 | what stopped it | a golf ball on a putting green | L02-q2 toy truck on tiles |
| PP-12 | easy | 002 | which force acted against the rolling | a ball on a field | PR-2 soccer ball on a parking lot (new ask: the force among four) |
| PP-13 | easy | 003 | farthest of four surfaces | a coin: blanket, gravel, glass, doormat | L03 bare pairs (two options → four) |
| PP-14 | easy | 003 | most friction of four surfaces | a box: wood, ice, a doormat, tile | NEW move |
| PP-15 | easy | 003 | sooner of two surfaces | a bar of soap: bathroom tiles / a bath mat | L03-q4 tile / rug ('farther' → 'sooner') |
| PP-16 | easy | 003 | true of a rougher surface | none | L03-q3 which has more friction |
| PP-17 | easy | 005 | odd one of four (unhelpful) | hooves, tires on a hill, a sticking door, hands on a rope | L04 quiz sort (two options → odd one of four) |
| PP-18 | easy | 005 | odd one of four (helpful) | chain, sliding door, drawer, sneaker on a court | L04-q2 gymnast's chalk |
| PP-19 | medium | 001 | direction of friction | a sled sliding left | PP-6 (new direction) |
| PP-20 | medium | 001 | locate friction where the rubbing pair is not a floor | hands sliding down a climbing rope | NEW move |
| PP-21 | medium | 001 | which force works against the push | a trunk across an attic floor | L01 headache (Elena's box) — the bank's one item on the headache MOVE, new scene |
| PP-22 | medium | 002 | why it goes far (little friction) | a curling stone on ice | L02-q7 hockey puck on ice |
| PP-23 | medium | 002 | what happens next | a toy tractor on a porch | L02-q8 wagon on the sidewalk |
| PP-24 | medium | 002 | what stopped it | an ice cube on a baking tray | L02-q2 |
| PP-25 | medium | 002 | FOR-02: why it keeps rolling, nobody pushing | a wagon on a smooth path | L02-q5 skateboard |
| PP-26 | medium | 002 | why it stopped (reasons) | a checker flicked on a board | L02-q6 coin on a tablecloth |
| PP-27 | medium | 002 | FOR-01 claim with the verdict fixed, four distinct statements | Reed's hockey puck and his stick | L02-q4 Darnell's marble |
| PP-28 | medium | 003 | reason for the distance difference | a sled: packed snow / gravel | L03-q9 cork on glass / towel |
| PP-29 | medium | 003 | choose the change that lowers friction | a toy boat on a deck | NEW move |
| PP-30 | medium | 003 | distances as evidence of less friction | a puck: 3 m / 9 m | NEW move |
| PP-31 | medium | 003 | reason for the distance difference | an eraser: desk / notebook cover | L03-q9 |
| PP-32 | medium | 003 | shorter distance → more friction, as a four-option MCQ (v2: was typed; medium) | two blocks: mat / tile | L03-q3 which has more friction |
| PP-33 | medium | 005 | why a change helps (more friction) | sand on icy steps | NEW move |
| PP-34 | medium | 005 | why rubber soles | runners' shoes | L04 video runner's shoes (new ask: the reason) |
| PP-35 | medium | 005 | what oil did to friction | a gate hinge | L04 article hinge (new move: the change) |
| PP-36 | medium | 005 | who wants more friction | skier, slide, curler, gymnast on a mat | NEW move |
| PP-37 | medium | 005 | FOR-08: the true sentence about friction | none | L04-q11 Carmen's claim |
| PP-38 | medium | 005 | odd one of four (helpful) | window, chalked hand on a wall, rusty wheel, drawer | PP-18 |
| PP-39 | medium | 005 | why friction helps where the slowing is wanted (v2: was a typed verdict) | a roller skate's rubber stopper on a sidewalk | L04 article brake (a slowing case on a new thing) |
| PP-40 | hard | 001 | type the name from the definition | a toboggan on snow | L01-q11 pencil case |
| PP-41 | hard | 002 | type the name from the stopping rule | none | PR-13 library book |
| PP-42 | hard | 002 | one force behind two distances | two balls: doormat / floor | NEW move |
| PP-43 | hard | 002 | judge 'nothing was pushing it along' (FOR-02) against FOR-01 and by-itself | a rolling ball | L02-q4, L02-q5 |
| PP-44 | hard | 003 | FOR-12 claim, verdict fixed, reasons (v2: tagged hard — a claim's reason is judged) | a toy car: mat / tiles | L03-q10 Reed's deck / lawn |
| PP-45 | hard | 003 | order four distances → smoothest | a cup: towel, cardboard, tile, ice | NEW move |
| PP-46 | hard | 003 | choose the change that lowers friction (four changes) | Reed's toy robot: hall floor / doormat | PP-28 (different scene kind: a floor, four changes) |
| PP-47 | hard | 003 | which of four has more friction than a fifth surface (v2: was a multi-select) | ice, tile, sandpaper, glass against a wool rug | NEW move |
| PP-48 | hard | 005 | choose the change that lowers friction where the sliding is wanted (v2: was a typed verdict) | a sliding glass door on its track | PP-17's sliding door option |
| PP-49 | hard | 005 | one force across three scenes | shoe, brake, drawer | NEW move |
| PP-50 | hard | 005 | judge a claim about an imagined removal | walking without friction | NEW move |
Draw constraints (⟂): PP-5 ⟂ PP-40 / 41 / 49 (the recognition item prints the typed items' key among its options); PP-16 ⟂ PP-14 (the rule sentence
answers the most-friction item). The test builder draws one of each pair per test. (v2: the doorway-recall item that was ⟂ the what-stopped-it item was cut.)
⟂ added after the v2 re-read (2 Oct 2026): PP-22 ⟂ PP-25 (same key wording, "Only a little friction pushes against it").