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Riding a bike: why it stays up

Tests: 5 of 11 right · Exam: 1 of 4 right · Kind: ★★ · Understood: 6 of 15 · Run: 2026-10-18, commit f3c23ea72

Lesson 9 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 ✓

My friend says a bike stays up cos the wheels spin like a top. right?

  • 1. Yes, that is the one magic trick — no support
  • 2. No, it is the air in the tyres — no support
  • 3. Yes, it is only the spinning — no support
  • 4. Not really, it is mostly steering and the bike's shape — ← Mova's choice · ✓ the right answer · score 1

Why: It took the question to ask which statement is true. It chose option 4 with score 1, the only option with support. Its support: lesson 9, line 1: «A bike stays up not by holding still but by steering: whenever it starts to tip, you turn the front wheel a little into the lean and bring the wheels back unde…», reached through the same lesson line as the sentence the question matched. What matched: the same action «steer» (+2); the same doer «bike» (+2). Against it: one says «not», the other does not (counts against) (-3). · the question and its options parsed, with trees and pragmatics

Test 2 · ★★ · wrong ✗

Riding no-hands down a busy road is fine if you're good, innit?

  • 1. Yes, it is safer than holding on — ← Mova's choice · no support
  • 2. No, never do it in traffic — ✓ the right answer · no support
  • 3. Only on rainy days — no support
  • 4. Yes, if you are fast enough — 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 3 · ★★ · wrong ✗

You want to go fast on a flat road. Which gear?

  • 1. The lowest gear — ← Mova's choice · score 3
  • 2. A low gear — score 3
  • 3. No gear at all — no support
  • 4. A high gear — ✓ the right answer · score 3

Why: It took the question to ask which statement is true. It chose option 1 with score 3, tied with another option at 3 (the first shown, or the one claiming less beyond what it knows, wins). 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 remembered sentence the question matched. What matched: the same thing acted on «low gears» (+3). The right option, 4, scored 3. · the question and its options parsed, with trees and pragmatics

Test 4 · ★★ · right ✓

In a game a rider brakes hard with only the front brake on a steep hill and stops neatly. What would really happen?

  • 1. The rider could fly over the handlebars — ← Mova's choice · ✓ the right answer · no support
  • 2. The back wheel would lift the rider up — no support
  • 3. The bike would roll backwards — no support
  • 4. The bike would stop smoothly and safely in a second — 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 · ★★ · wrong ✗

Which bike would be best for a muddy forest track?

  • 1. A bike with no tyres, just the metal rims — ← Mova's choice · no support
  • 2. A bike with flat tyres that bump on the rim — no support
  • 3. A road bike with thin, smooth racing tyres — no support
  • 4. A mountain bike with wide knobbly tyres — ✓ 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 6 · ★★ · wrong ✗

Why do people wobble so much on a bike at walking speed?

  • 1. The bike is heavier when slow — ← Mova's choice · no support
  • 2. Slow riding needs bigger steering to stay up — ✓ the right answer · no support
  • 3. Slow wheels lose all their air — no support
  • 4. The pedals pull you sideways — 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 · ★★ · right ✓

A small wheel and a big wheel roll into the same stone. Which gets over it more easily?

  • 1. The big wheel — ← Mova's choice · ✓ the right answer · score 6
  • 2. The small wheel — score 6
  • 3. Both the same — no support
  • 4. Neither can get over it — no support

Why: It took the question to ask who or what does it. It chose option 1 with score 6, tied with another option at 6 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 9, line 14: «Big wheels roll over bumps easily, and thin, smooth tyres rub the road less.», reached through the option's own match among the sentences about the question's things. What matched: it fills the role the question asks for (+3); the same doer «big wheels» (+2); the same property (+1). · the question and its options parsed, with trees and pragmatics

Test 8 · ★★ · wrong ✗

bro my bike fell over when i stopped at the lights. why

  • 1. Bikes get heavier as soon as they stop moving — ← Mova's choice · no support
  • 2. Your tyres lost all of their air at once when you stopped — no support
  • 3. The traffic lights pulled it over with magnetism — no support
  • 4. With no speed you cannot steer to balance — ✓ 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 9 · ★★ · right ✓

What would happen if you leaned into a bend while going very slowly?

  • 1. You would suddenly go a lot faster — no support
  • 2. You would tip over inwards — ← Mova's choice · ✓ the right answer · score 2
  • 3. Nothing at all would happen to you — no support
  • 4. You would fall outwards away from the bend — no support

Why: It took the question to ask what happens next. It chose option 2 with score 2, the only option with support. Its support: lesson 9, line 11: «Cyclists lean into a corner to balance the sideways push of the ground on their tyres; turning sharply without leaning makes you fall outwards, and leaning har…», reached through the option's own match among the sentences about the question's things. What matched: the same action «tip over» (+2); the same property (+1). Against it: a different doer (counts against) (-1). · the question and its options parsed, with trees and pragmatics

Test 10 · ★★ · wrong ✗

Why do skilled riders sit back on steep downhill slopes?

  • 1. It makes the brakes cooler — ← Mova's choice · no support
  • 2. It keeps their weight from tipping over the front — ✓ the right answer · no support
  • 3. It makes them faster — no support
  • 4. It makes the hill less steep — 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 11 · ★★ · right ✓

A tyre goes flat and the rim bumps on the road. Why did it feel hard before?

  • 1. Many air molecules pushed on the rubber — ← Mova's choice · ✓ the right answer · score 10
  • 2. The rubber was frozen solid by the cold air pumped into it — no support
  • 3. The metal inside was bigger — no support
  • 4. The tyre was full of water — score 6

Why: It took the question to ask why something happens (its cause). It chose option 1 with score 10, against 6 for the next best. Its support: lesson 9, line 16: «A bike pump gets warm because squashing air quickly warms it, and a pumped tyre is hard because many air molecules (tiny bits of air) push on the rubber.», reached through the cause of the sentence the question matched. What matched: the same circumstance (+6); the same action «push» (+4). · the question and its options parsed, with trees and pragmatics

Exam question 1 · formal language · right ✓

Identify the principal means by which a cyclist maintains equilibrium upon a moving bicycle.

  • 1. By the gyroscopic action of the pedals alone — no support
  • 2. By the upward pressure of the air upon the frame — no support
  • 3. By keeping the body perfectly motionless upon the saddle — no support
  • 4. By steering the front wheel into any incipient lean — ← Mova's choice · ✓ the right answer · score 4

Why: It took the question to ask which statement is true. It chose option 4 with score 4, the only option with support. Its support: lesson 9, line 6: «A moving bike stays up because the rider steers into any lean and brings the wheels back under the centre of gravity.», reached through the same lesson line as the sentence the question matched. What matched: the same action «steer» (+2); the same place «lean» (+2). · the question and its options parsed, with trees and pragmatics

Exam question 2 · formal language · wrong ✗

Which of the following statements most accurately characterises the effect of a low gear upon the ascent of a hill?

  • 1. The mass of the bicycle is effectively diminished — ← Mova's choice · no support
  • 2. The incline of the hill is effectively diminished — no support
  • 3. Each push is harder, but fewer revolutions are required — no support
  • 4. Each push is gentler, but a greater number of revolutions is required — ✓ 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 3 · formal language · wrong ✗

It is given that a cyclist applies the front brake alone and with great force. Ascertain the hazard thereby occasioned.

  • 1. The pedals may be caused to rotate in reverse — ← Mova's choice · no support
  • 2. The rider may be projected over the handlebars — ✓ the right answer · no support
  • 3. The rear wheel may be inflated beyond its limit — no support
  • 4. The frame may be rendered incapable of steering — 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 a stationary bicycle without support falls over.

  • 1. The tyres lose their air when at rest — ← Mova's choice · no support
  • 2. Its centre of gravity is located beneath the ground — no support
  • 3. No forward motion is available by which to steer beneath the lean — ✓ the right answer · no support
  • 4. The frame becomes heavier when stationary — 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

This page in Markdown → https://md.mova.elamur.ai/free/en/school-run/physics/9-riding-a-bike/