Floating and sinking: the push of water

Tests: 4 of 13 right · Exam: 3 of 4 right · Kind: ★ · Understood: 16 of 17 · Run: 2026-10-18, commit f3c23ea72

Lesson 83 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 · ★ · right ✓

An egg sinks in a glass of tap water. You stir in lots of salt and the egg rises. Why?

1. The stirring pushes the egg up for good and it stays there — no support
2. The salt makes the egg lighter inside — no support
3. The salt sticks to the egg and lifts it — no support
4. The salty water pushes up harder on the egg — ← Mova's choice · ✓ the right answer · score -1

Why: It took the question to ask why something happens (its cause). It chose option 4 with score -1, the only option with support. Its support: lesson 29, line 3: «A penguin cannot fly and swims like a fish, but it has feathers and lays eggs with hard shells, so it is a bird.», reached through the option's own match among the sentences about the question's things. What matched: the same property (+1). Against it: the same circumstance (-1); a different doer (counts against) (-1). · the question and its options parsed, with trees and pragmatics

Test 2 · ★ · wrong ✗

Which is true about a floating object?

1. It floats only because it contains air, which has no weight — score 5
2. It pushes aside no water at all — ← Mova's choice · score 7
3. The water it pushes aside weighs the same as it does — ✓ the right answer · score 4
4. It has no weight while it floats — score 5

Why: It took the question to ask which statement is true. It chose option 2 with score 7, against 5 for the next best. Its support: lesson 83, line 7: «A floating object pushes aside, or displaces, some water.», reached through the remembered sentence the question matched. What matched: the same action «push» (+4); the same property (+2); the same doer «floating object» (+1). The right option, 3, scored 4. · the question and its options parsed, with trees and pragmatics

Test 3 · ★ · wrong ✗

A sailor watches a cargo ship as its boxes are taken off in port. What does the sailor see?

1. The ship slowly sinks lower in the water — ← Mova's choice · score 5
2. The ship slowly rises higher in the water — ✓ the right answer · score 0
3. The ship stays exactly where it was in the water — score 2
4. The ship tips over onto one side — no support

Why: It took the question to ask what it is done to. It chose option 1 with score 5, against 2 for the next best. Its support: lesson 7, line 4: «People knew the Earth was round more than two thousand years ago: ships sink hull first (the hull is the bottom part of a ship) below the horizon, the far line…», reached through the option's own match among the sentences about the question's things. What matched: the same action «sink» (+4); the same doer «ships» (+1). The right option, 2, scored 0. · the question and its options parsed, with trees and pragmatics

Test 4 · ★ · right ✓

You squeeze a ball of foil tightly into a tiny lump. It sinks, though a loose foil boat floats. Why?

1. Squeezing it makes the foil much heavier than before — no support
2. The boat floats only because its inside stays dry — no support
3. The tight lump pushes aside too little water — ← Mova's choice · ✓ the right answer · score 10
4. Squeezing turns the foil into a new and heavier metal — no support

Why: It took the question to ask why something happens (its cause). It chose option 3 with score 10, the only option with support. Its support: lesson 83, line 3: «If the upthrust can grow as big as the object's weight, the object floats; if the object sinks fully under and the upthrust is still smaller than its weight, i…», reached through the option's own match among the sentences about the question's things. What matched: the same action «push» (+3); the same doer «lump» (+3); the same thing acted on «more water» (+3); the same property (+1). · the question and its options parsed, with trees and pragmatics

Test 5 · ★ · wrong ✗

A boat sails from a river into the sea. What happens?

1. It floats a little lower in the salty sea — ← Mova's choice · score 2
2. It must take on water to stay balanced — no support
3. It floats at exactly the same height — no support
4. It floats a little higher in the salty sea — ✓ the right answer · score 2

Why: It took the question to ask what happens next. It chose option 1 with score 2, tied with another option at 2 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 83, line 4: «Salty water is heavier than the same amount of fresh water, so it pushes up harder. That is why people float easily in the very salty Dead Sea, and why a ship…», reached through the option's own match among the sentences about the question's things. What matched: the same action «float» (+2); the same place «salty dead sea» (+1). Against it: a different doer (counts against) (-1). The right option, 4, scored 2. · the question and its options parsed, with trees and pragmatics

Test 6 · ★ · right ✓

What would happen to a pond in winter if ice were denser than water?

1. Ice would sink and the pond could freeze from the bottom up — ← Mova's choice · ✓ the right answer · score 4
2. The pond could never freeze at all — score 3
3. Ice would float even higher than it does now, right on top of the pond — score 4
4. The ice would turn back into water at once — score 1

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 18, line 11: «An object floats if it is less dense than water, and sinks if it is denser.», reached through what followed the sentence the question matched. What matched: the same action «sink» (+5). Against it: a different doer (counts against) (-1). · the question and its options parsed, with trees and pragmatics

Test 7 · ★ · wrong ✗

A diver wants to stay still in the middle of the water. What should be true?

1. The diver must weigh nothing in the water — ← Mova's choice · no support
2. The upthrust must be much bigger than the weight — no support
3. The upthrust must equal the diver's weight — ✓ the right answer · no support
4. The diver must breathe out all the air — 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 8 · ★ · wrong ✗

Which object is most likely to float?

1. A small solid lump of iron — ← Mova's choice · score 7
2. A big hollow plastic box with its lid shut — ✓ the right answer · no support
3. A handful of coins — no support
4. A glass marble — no support

Why: It took the question to ask who or what does it. It chose option 1 with score 7, the only option with support. Its support: lesson 83, line 3: «If the upthrust can grow as big as the object's weight, the object floats; if the object sinks fully under and the upthrust is still smaller than its weight, i…», reached through the same lesson line as the sentence the question matched. What matched: it fills the role the question asks for (+4); the same doer «lump» (+3). The right option, 2, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 9 · ★ · wrong ✗

Why would a submarine with empty tanks find it hard to stay under water?

1. It would be too heavy and would fall too fast — score 4
2. Empty tanks stop the propeller from turning — no support
3. Its engine needs water in the tanks to work at all, so it stops — ← Mova's choice · score 5
4. It would be too light, so the upthrust pushes it up — ✓ the right answer · score 4

Why: It took the question to ask why something happens (its cause). It chose option 3 with score 5, against 4 for the next best. Its support: lesson 25, line 17: «When a seed starts to grow it is called germination; it needs water, air and warmth.», reached through the option's own match among the sentences about the question's things. What matched: the same action «need» (+3); the same thing acted on «water» (+3). 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 10 · ★ · right ✓

how does a massive steel ship float when a nail sinks

1. Air from the sea holds the ship up — no support
2. Steel floats once it is very big — no support
3. The engines push it up out of the water — no support
4. Its hollow shape pushes aside lots of water, giving enough upthrust — ← 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 3: «If the upthrust can grow as big as the object's weight, the object floats; if the object sinks fully under and the upthrust is still smaller than its weight, i…», reached through a sentence linked to the one the question matched. What matched: the same action «push» (+4); the same property (+2); a different doer (counts against) (+1). Against it: a different thing acted on (counts against) (-1). · the question and its options parsed, with trees and pragmatics

Test 11 · ★ · wrong ✗

why does the boat sit lower when u load it up

1. The cargo pulls the water down with it — ← Mova's choice · score 3
2. The water gets thinner under heavy boats, so they sink lower — no support
3. Heavy boats leak and fill with water — no support
4. More weight means it must push aside more water to float — ✓ the right answer · no support

Why: It took the question to ask which statement is true. It chose option 1 with score 3, the only option with support. Its support: lesson 83, line 4: «Salty water is heavier than the same amount of fresh water, so it pushes up harder. That is why people float easily in the very salty Dead Sea, and why a ship…», reached through the same lesson line as the sentence the question matched. What matched: the same thing acted on «fresh water» (+2); the same circumstance (+2). Against it: a different action (counts against) (-1). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 12 · ★ · wrong ✗

Ava says ice floats cos it's got air bubbles in it. true?

1. No, ice floats because it is colder than the water — ← Mova's choice · score 9
2. Yes, ice without bubbles always sinks — no support
3. Yes, only the bubbles keep ice up — no support
4. No, water expands when it freezes, so ice is lighter than the same amount of water — ✓ the right answer · score 9

Why: It took the question to ask which statement is true. It chose option 1 with score 9, tied with another option at 9 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 83, line 15: «Ice floats because water expands when it freezes, so ice is lighter than the same amount of water.», reached through the remembered sentence the question matched. What matched: the same action «float» (+4); its «because» matches the remembered cause (+4); the same doer «ice» (+1). The right option, 4, scored 9. · the question and its options parsed, with trees and pragmatics

Test 13 · ★ · wrong ✗

my brother reckons it's easier to float in a pool than in the sea. right?

1. Yes, but only if the pool is heated — no support
2. No, both give exactly the same upthrust — no support
3. Yes, fresh water pushes up harder than salt water — ← Mova's choice · score 7
4. No, salt water gives more upthrust than fresh water — ✓ the right answer · no support

Why: It took the question to ask which statement is true. It chose option 3 with score 7, the only option with support. Its support: lesson 83, line 4: «Salty water is heavier than the same amount of fresh water, so it pushes up harder. That is why people float easily in the very salty Dead Sea, and why a ship…», reached through the same lesson line as the sentence the question matched. What matched: the same action «push up» (+3); the same doer «water» (+3); the same property (+1). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Exam question 1 · formal language · right ✓

Which of the following statements most accurately characterises upthrust?

1. The push of water upwards upon an object placed in it — ← Mova's choice · ✓ the right answer · score 7
2. The friction between a boat and the water — no support
3. The pull of the Earth downwards upon an object — no support
4. The weight of an object measured in air — no support

Why: It took the question to ask who or what does it. It chose option 1 with score 7, the only option with support. Its support: lesson 30, line 5: «To guess what happens when one living thing disappears, follow the arrows: what it ate will grow in number, what ate it will go hungry and must switch food, sh…», reached through the same lesson line as the sentence the question matched. What matched: it fills the role the question asks for (+4); the same doer «thing» (+3). · the question and its options parsed, with trees and pragmatics

Exam question 2 · formal language · wrong ✗

It is given that cargo is loaded upon a ship. Determine the consequent alteration in its position in the water.

1. It sits higher in the water — ← Mova's choice · score 7
2. It remains at exactly the same level — no support
3. It rises entirely out of the water — no support
4. It sits lower in the water — ✓ the right answer · score 7

Why: It took the question to ask which statement is true. It chose option 1 with score 7, tied with another option at 7 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 83, line 11: «The more cargo a ship carries, the lower it sits in the water.», reached through a sentence linked to the one the question matched. What matched: the same action «sit» (+4); the same place «water» (+2); a different doer (counts against) (+1). The right option, 4, scored 7. · the question and its options parsed, with trees and pragmatics

Exam question 3 · formal language · right ✓

Identify the principal reason for which ice floats upon water.

1. Water expands when frozen, so ice is lighter than the same amount of water — ← Mova's choice · ✓ the right answer · score 9
2. Ice possesses no weight whatsoever — score 1
3. Ice contains bubbles of a gas lighter than air — score 4
4. Ice is pushed upwards by the cold of the water — score 3

Why: It took the question to ask which statement is true. It chose option 1 with score 9, against 4 for the next best. Its support: lesson 83, line 15: «Ice floats because water expands when it freezes, so ice is lighter than the same amount of water.», reached through the same lesson line as the sentence the question matched. What matched: the same doer «ice» (+3); the same circumstance (+2); its «because» matches the remembered cause (+2); the same property (+1). · 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 upthrust of salt water and fresh water.

1. Salt water gives more upthrust than fresh water — ← Mova's choice · ✓ the right answer · score 6
2. Salt water gives no upthrust whatsoever — score 6
3. Both give exactly the same upthrust — score 3
4. Fresh water gives more upthrust than salt water — score 6

Why: It took the question to ask which statement is true. 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 83, line 12: «Salt water gives more upthrust than fresh water.», reached through the remembered sentence the question matched. What matched: the same action «give» (+4); the same doer «salt water» (+1); the same thing acted on «more upthrust» (+1). · the question and its options parsed, with trees and pragmatics

This page in Markdown → https://md.mova.elamur.ai/free/en/school-run/world/83-floating-and-sinking/