Friction: the grip that stops and helps
Tests: 5 of 11 right · Exam: 0 of 4 right · Kind: plain · Understood: 6 of 15 · Run: 2026-10-18, commit f3c23ea72
Lesson 6 of the physics course of Mova's primary school, as Mova's small model took its tests: it had read this lesson and the ones before it and learned from their exercises. Each test shows the options in the order the student saw them, its choice, the right answer, the score of every option and why it chose. The lesson itself, sentence by sentence with trees and pragmatics: the lesson in the corpora.
Every question of this lesson and each of its options parsed by Mova, with trees and pragmatics: the lesson's questions in the corpora.
Test 1 · right ✓
whyyy do my hands get warm when i rub em, is it magic
- 1. Yes, rubbing makes your hands a bit magnetic — no support
- 2. Your hands catch the room's heat — no support
- 3. Your blood boils a little — no support
- 4. No, friction turns the rubbing into heat — ← Mova's choice · ✓ the right answer · score 5
Why: It took the question to ask which statement is true. It chose option 4 with score 5, the only option with support. Its support: lesson 6, line 4: «Rub your hands together on a cold day and they warm up: friction always turns some movement into heat.», reached through the same lesson line as the sentence the question matched. What matched: the same action «turn» (+2); the same doer «friction» (+2); the same place «heat» (+2). Against it: a different thing acted on (counts against) (-1). · the question and its options parsed, with trees and pragmatics
Test 2 · right ✓
In a cartoon a boy brakes his bike hard in the rain and stops at once. What is closer to the truth?
- 1. Wet brakes grip much better — score 5
- 2. Rain makes the bike stop by itself — no support
- 3. Wet brakes grip less, so he needs longer to stop — ← Mova's choice · ✓ the right answer · score 6
- 4. Brakes do not work at all in rain — score 1
Why: It took the question to ask which statement is true. It chose option 3 with score 6, against 5 for the next best. Its support: lesson 6, line 11: «Wet brakes grip less, so you must brake earlier in the rain.», reached through a sentence linked to the one the question matched. What matched: the same action «grip» (+3); the same doer «wet brakes» (+2); the same property (+1). · the question and its options parsed, with trees and pragmatics
Test 3 · right ✓
Why do climbers wear gloves when a rope runs through their hands?
- 1. Gloves stop the rope getting wet from sweat — no support
- 2. A fast rope can burn the skin by friction — ← Mova's choice · ✓ the right answer · score 6
- 3. Gloves make the rope lighter — no support
- 4. Ropes are too cold to touch — no support
Why: It took the question to ask why something happens (its cause). It chose option 2 with score 6, the only option with support. Its support: lesson 6, line 9: «Rubbing your hands makes friction, and friction turns movement into heat; a rope rushing through your hands can even burn them.», reached through the same lesson line as the sentence the question matched. What matched: the same action «burn» (+3); the same doer «rope» (+3). · the question and its options parsed, with trees and pragmatics
Test 4 · right ✓
A heavy box will not slide across the carpet. What trick helps most?
- 1. Put it on a rug and drag the rug on a smooth floor — ← Mova's choice · ✓ the right answer · no support
- 2. Add more weight on top — no support
- 3. Wet the carpet first — no support
- 4. Push it harder from the top — no support
Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
Test 5 · right ✓
Why do drivers use low gears on long mountain roads?
- 1. So the car goes faster downhill — no support
- 2. To save petrol going down — no support
- 3. So the brakes do not get too hot — ← Mova's choice · ✓ the right answer · score 2
- 4. Because high gears break on hills — no support
Why: It took the question to ask why something happens (its cause). It chose option 3 with score 2, the only option with support. Its support: lesson 6, line 13: «On long mountain roads car brakes can get so hot that they stop working well, so drivers use low gears.», reached through the same lesson line as the sentence the question matched. What matched: the same doer «car brakes» (+3); the same property (+1); the same light verb (be, have, do, get, go) (+1). Against it: one says «not», the other does not (counts against) (-3). · the question and its options parsed, with trees and pragmatics
Test 6 · wrong ✗
What would happen if you tried to stop quickly on a polished floor in socks?
- 1. You would stick to the floor — ← Mova's choice · no support
- 2. You would stop at once — no support
- 3. You would bounce back — no support
- 4. You would slide on — ✓ the right answer · no support
Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
Test 7 · wrong ✗
What is aquaplaning?
- 1. A plane landing on the sea — ← Mova's choice · no support
- 2. A tyre filling up with water — no support
- 3. A car sliding on a layer of water under its tyres — ✓ the right answer · no support
- 4. A boat going very fast — no support
Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
Test 8 · wrong ✗
Why are matches kept away from children?
- 1. They are too heavy for children — no support
- 2. They taste of chemicals — no support
- 3. One quick rub makes real fire — ✓ the right answer · no support
- 4. They break too easily — ← Mova's choice · score 5
Why: It took the question to ask why something happens (its cause). It chose option 4 with score 5, the only option with support. Its support: lesson 6, line 17: «A match bursts into flame because one quick rub on the rough strip makes enough heat to set off the chemicals on its head.», reached through the option's own match among the sentences about the question's things. What matched: the same action «burst» (+3); the same doer «match» (+2). The right option, 3, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics
Test 9 · wrong ✗
A hot sticky day, bare legs on a metal slide. What happens?
- 1. You slide twice as fast — ← Mova's choice · no support
- 2. Nothing changes on hot days — no support
- 3. Your skin grips and squeaks and you slow down — ✓ the right answer · no support
- 4. The slide gets slippery — no support
Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
Test 10 · wrong ✗
Gran says brakes get hot cos the sun shines on them. right?
- 1. No, brakes get cold when used — ← Mova's choice · score 4
- 2. No, friction turns the speed into heat — ✓ the right answer · score 3
- 3. Yes, black brakes always get hot — score 4
- 4. Yes, dark brakes soak up the sunshine all day — no support
Why: It took the question to ask which statement is true. It chose option 1 with score 4, tied with another option at 4 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 6, line 5: «Bike brakes use this too, squeezing rubber pads against the wheel until the speed turns into heat.», reached through the option's own match among the sentences about the question's things. What matched: the same action «use» (+2); the same doer «bike brakes» (+2). The right option, 2, scored 3. · the question and its options parsed, with trees and pragmatics
Test 11 · wrong ✗
Which pair has the most friction?
- 1. Socks sliding on a polished floor — ← Mova's choice · no support
- 2. A sledge running on fresh snow — no support
- 3. Skates gliding over smooth ice — no support
- 4. Rubber soles on a rough path — ✓ the right answer · no support
Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
Exam question 1 · formal language · wrong ✗
Which of the following statements most accurately characterises the phenomenon designated friction?
- 1. The tendency of bodies to rise in water — ← Mova's choice · no support
- 2. The attraction of bodies towards the centre of the Earth — no support
- 3. The resistance to sliding between two surfaces in contact — ✓ the right answer · no support
- 4. The resistance of the air to all motion — no support
Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
Exam question 2 · formal language · wrong ✗
Identify the principal reason for which the brakes of a bicycle are rendered less effective in wet conditions.
- 1. Water causes the tyres to become inflated — ← Mova's choice · no support
- 2. Water increases the mass of the wheel — no support
- 3. Water between pad and rim diminishes their grip — ✓ the right answer · no support
- 4. Water lowers the temperature of the rider's hands — no support
Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
Exam question 3 · formal language · wrong ✗
It is given that a cyclist descends a long hill with the brakes applied. Ascertain the form into which the energy of motion so lost is principally converted.
- 1. Sound in the air surrounding the bicycle — ← Mova's choice · no support
- 2. Light emitted by the pads in braking — no support
- 3. Heat in the brake pads and rims — ✓ the right answer · no support
- 4. Additional mass acquired by the wheels — no support
Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
Exam question 4 · formal language · wrong ✗
Determine the reason for which sand is distributed upon icy footpaths.
- 1. It renders the ice transparent — ← Mova's choice · no support
- 2. It increases the thickness of the ice beneath — no support
- 3. It furnishes a rough surface affording grip — ✓ the right answer · no support
- 4. It raises the temperature of the path — no support
Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics
This page in Markdown → https://md.mova.elamur.ai/free/en/school-run/physics/6-friction-the-grip/