Pushes, pulls, friction and wheels

Tests: 6 of 13 right · Exam: 3 of 4 right · Kind: ★ · Understood: 12 of 17 · Run: 2026-10-18, commit f3c23ea72

Lesson 85 of the world 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 · ★ · wrong ✗

A car moves along a straight road at a steady speed. Which is true?

1. The forward force is much bigger — ← Mova's choice · no support
2. The forward and backward forces are balanced — ✓ the right answer · no support
3. There are no forces on the car at all — no support
4. The backward force is much bigger — 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 2 · ★ · wrong ✗

What would happen if there were no friction at all?

1. Wheels would turn much more slowly — ← Mova's choice · score 4
2. Everything would stop moving at once — no support
3. Things would become much heavier — score 4
4. You could not walk without slipping — ✓ the right answer · score 4

Why: It took the question to ask what happens next. 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 85, line 3: «Friction can be a helper or a nuisance. It lets tyres grip the road, shoes grip the floor and brakes stop a bike. But it also wears things out and turns moveme…», reached through what followed the sentence the question matched. What matched: the same action «turn» (+5). Against it: a different doer (counts against) (-1). The right option, 4, scored 4. · the question and its options parsed, with trees and pragmatics

Test 3 · ★ · right ✓

Ancient builders moved huge stones by rolling them on logs. Why did this help?

1. Rolling makes less friction than dragging — ← Mova's choice · ✓ the right answer · score 5
2. The logs pushed the stones uphill — no support
3. The logs pulled the stones forwards — no support
4. The logs made the stones lighter — no support

Why: It took the question to ask which statement is true. It chose option 1 with score 5, the only option with support. Its support: lesson 85, line 4: «A wheel makes moving heavy things much easier, because rolling makes far less friction than sliding. Dragging a heavy box across a floor is hard, but the same…», reached through the same lesson line as the sentence the question matched. What matched: the same action «make» (+3); the same thing acted on «less friction» (+2). · the question and its options parsed, with trees and pragmatics

Test 4 · ★ · wrong ✗

A cyclist squeezes the brakes. How do the brakes stop the bike?

1. They make the bike heavier — ← Mova's choice · score 2
2. They let all the air out of both of the tyres — no support
3. They push the wheel forwards faster — no support
4. They rub on the wheel and make friction — ✓ the right answer · no support

Why: It took the question to ask what something is like. It chose option 1 with score 2, the only option with support. Its support: lesson 85, line 3: «Friction can be a helper or a nuisance. It lets tyres grip the road, shoes grip the floor and brakes stop a bike. But it also wears things out and turns moveme…», reached through the remembered sentence the question matched. What matched: the same doer «brakes» (+3); the same thing acted on «bike» (+3). Against it: a different action (counts against) (-4). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 5 · ★ · right ✓

Which is a case where we want less friction?

1. A door hinge that squeaks — ← Mova's choice · ✓ the right answer · no support
2. Brakes on a bicycle — no support
3. Tyres on a wet road — no support
4. The soles of running shoes — 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 6 · ★ · wrong ✗

A truck and a bicycle are moving at the same speed. Which needs a bigger force to stop?

1. Both need exactly the same force — ← Mova's choice · score 4
2. The bicycle, because it is lighter and thinner — no support
3. The truck, because it is much heavier — ✓ the right answer · no support
4. Neither needs any force to stop — score 4

Why: It took the question to ask who or what does it. 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 85, line 10: «Heavier objects need a bigger force to start them moving or to stop them.», reached through the option's own match among the sentences about the question's things. What matched: the same thing acted on «bigger force» (+4); the same action «need» (+2). Against it: a different doer (counts against) (-2). The right option, 3, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 7 · ★ · wrong ✗

A toy car is pushed on smooth tiles and on thick carpet with the same push. Where does it roll further?

1. On the smooth tiles — ✓ the right answer · no support
2. On the thick carpet — no support
3. It cannot roll on either — no support
4. Exactly the same on both — ← Mova's choice · score 1

Why: It took the question to ask where. It chose option 4 with score 1, the only option with support. Its support: lesson 85, line 4: «A wheel makes moving heavy things much easier, because rolling makes far less friction than sliding. Dragging a heavy box across a floor is hard, but the same…», reached through the remembered sentence the question matched. What matched: the same action «roll» (+3). Against it: the same property (-1); a different doer (counts against) (-1). The right option, 1, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 8 · ★ · wrong ✗

Why are worn, smooth tyres dangerous on a rainy day?

1. They make the brakes work too hard — ← Mova's choice · no support
2. They are much heavier than new tyres — no support
3. They cannot push the water away to grip — ✓ the right answer · no support
4. They make the car go too slowly — 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 9 · ★ · right ✓

You hang a heavier bag on a forcemeter. What happens?

1. The spring stretches further — ← Mova's choice · ✓ the right answer · no support
2. The spring gets shorter and squashes — no support
3. The spring stays exactly the same — no support
4. The spring stretches less than before — 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 10 · ★ · right ✓

why's oil put on a squeaky bike chain

1. Oil reduces friction between the moving parts — ← Mova's choice · ✓ the right answer · score 7
2. Oil makes the chain heavier so it runs steadily — no support
3. Oil makes the chain grip the wheel harder — no support
4. Oil keeps the chain warm in winter — no support

Why: It took the question to ask which statement is true. It chose option 1 with score 7, the only option with support. Its support: lesson 85, line 13: «Oil and grease reduce friction between moving parts.», reached through the option's own match among the sentences about the question's things. What matched: the same action «reduce» (+3); the same doer «oil» (+2); the same circumstance (+2). · the question and its options parsed, with trees and pragmatics

Test 11 · ★ · right ✓

why'd i fly forward when the bus braked hard

1. Your body keeps moving forwards when the bus stops — ← Mova's choice · ✓ the right answer · score 7
2. The bus pushed you forwards really hard as it braked — no support
3. The air in the bus blew you forwards — no support
4. Gravity pulled you towards the front — no support

Why: It took the question to ask which statement is true. It chose option 1 with score 7, the only option with support. Its support: lesson 85, line 2: «A moving object keeps moving until a force stops it. A puck slides a long way on ice because there is little friction to slow it. In a car that brakes suddenly…», reached through the same lesson line as the sentence the question matched. What matched: the same action «move» (+3); the same doer «body» (+3); the same property (+1). · the question and its options parsed, with trees and pragmatics

Test 12 · ★ · right ✓

Leo says a moving thing just stops by itself if nothing pushes it. true?

1. Yes, all moving things slow down on their own — no support
2. Yes, but only heavy things stop by themselves — no support
3. No, a moving thing never stops at all — no support
4. No, it keeps moving until a force such as friction stops it — ← Mova's choice · ✓ the right answer · score 6

Why: It took the question to ask which statement is true. It chose option 4 with score 6, the only option with support. Its support: lesson 83, line 2: «An object in water pushes some water out of the way; we say it displaces the water. The upthrust is equal to the weight of the water pushed aside. This was dis…», reached through the same lesson line as the sentence the question matched. What matched: the same action «displace» (+3); the same doer «water» (+3). · the question and its options parsed, with trees and pragmatics

Test 13 · ★ · wrong ✗

my sister reckons friction is always bad. right?

1. No, friction helps tyres, shoes and brakes to grip — ✓ the right answer · score 5
2. No, friction only matters when things move through water — no support
3. Yes, friction only wears things out and wastes energy — score 5
4. Yes, cars would work better with no friction — ← Mova's choice · score 6

Why: It took the question to ask which statement is true. It chose option 4 with score 6, against 5 for the next best. Its support: lesson 51, line 3: «Friction is a force that appears when two surfaces rub against each other. It always works against the movement, so it slows things down and turns some of the…», reached through the remembered sentence the question matched. What matched: the same action «work» (+4); the same circumstance (+4). Against it: a different doer (counts against) (-2). The right option, 1, scored 5. · the question and its options parsed, with trees and pragmatics

Exam question 1 · formal language · right ✓

Which of the following statements most accurately characterises balanced forces?

1. They are equal and opposite and do not change an object's movement — ← Mova's choice · ✓ the right answer · score 13
2. They always cause an object to change direction — score 9
3. They act only upon objects at rest — score 9
4. They always cause an object to speed up — score 9

Why: It took the question to ask who or what does it. It chose option 1 with score 13, against 9 for the next best. Its support: lesson 85, line 6: «Balanced forces are equal and opposite, so they do not change an object's movement.», reached through the option's own match among the sentences about the question's things. What matched: the same thing acted on «movement» (+4); it fills the role the question asks for (+4); the same doer «forces» (+3); the same action «change» (+2). · the question and its options parsed, with trees and pragmatics

Exam question 2 · formal language · right ✓

It is given that a car stops suddenly. Identify the principal reason for which seat belts are required.

1. The friction of the seat ceases entirely — no support
2. The body is pushed backwards into the seat — no support
3. The body keeps moving forwards and must be held — ← Mova's choice · ✓ the right answer · score 6
4. Gravity becomes stronger at the moment of stopping — no support

Why: It took the question to ask which statement is true. It chose option 3 with score 6, the only option with support. Its support: lesson 85, line 2: «A moving object keeps moving until a force stops it. A puck slides a long way on ice because there is little friction to slow it. In a car that brakes suddenly…», reached through the same lesson line as the sentence the question matched. What matched: the same action «keep» (+3); the same doer «body» (+3). · the question and its options parsed, with trees and pragmatics

Exam question 3 · formal language · wrong ✗

Ascertain the unit in which forces are measured.

1. Kilograms — ← Mova's choice · no support
2. Newtons — ✓ the right answer · no support
3. Degrees — no support
4. Metres — 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 · right ✓

Select the response that is consistent with the established facts concerning the grooves in the tyres of a vehicle.

1. They render the tyres lighter for greater speed — no support
2. They push water away so the tyres can grip a wet road — ← Mova's choice · ✓ the right answer · score 7
3. They serve only as decoration — no support
4. They reduce the grip of the tyres upon the road — no support

Why: It took the question to ask which statement is true. It chose option 2 with score 7, the only option with support. Its support: lesson 85, line 16: «The grooves in tyres push water away so the tyres can grip a wet road.», reached through the option's own match among the sentences about the question's things. What matched: the same action «grip» (+3); the same doer «tyres» (+2); its «because» matches the remembered cause (+2). · the question and its options parsed, with trees and pragmatics

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