What is torque?
Torque is what turns things: a push times its distance from the pivot. Undo a stuck wheel nut, balance a seesaw, tip a double-decker bus, test an engine on a brake, crack a walnut, and watch a gyroscope refuse to fall.
▶ Play with it · Read the 60-second explainer · Watch the 40-second video
- Force times distance. Torque is the turning effect of a force: τ = F × r, in newton-metres. Only the part of the push at right angles counts, τ = F r sin θ. A stuck nut turns only when your torque beats its breakaway torque, and a door swings fastest when you push at the handle.
- Balance. An object stays still when the clockwise and anticlockwise moments match: m₁d₁ = m₂d₂ on a seesaw. It stands while the line down from its centre of gravity falls inside its base, which is why double-decker buses are tilted to 28° in a test. A tightrope walker's pole slows the fall.
- Machines that turn. A 17 cm bicycle crank turns your push into torque, and the gears change it at the wheel. On a test brake, a 1.2 litre engine makes about 113 N·m, a mixer under 1 N·m. Power is torque × spin speed, P = τω, so the fast little mixer still makes hundreds of watts.
- Torque in your hands. When a job needs a set torque, a bigger radius means less force: steering wheels, fat screwdriver handles, nutcrackers and a pipe on a wheel brace. A torque wrench clicks at the right torque. Your biceps works the other way, pulling about nine times the load.
- Spin, wobble and myths. Unbalanced torque spins things up, τ = Iα. A gyroscope's torque swings its spin round instead of tipping it. Torque and work share N·m but differ: a stuck nut gets no joules. A longer spanner gives more torque, not more force, and speed comes from power, not torque.
| Term | Meaning |
|---|---|
| Torque | The turning effect of a force: force × distance from the pivot, at right angles. |
| Newton-metre (N·m) | The unit of torque: 1 newton pushing at right angles 1 metre from the pivot. |
| Lever arm | The shortest distance from the pivot to the line of a force, r sin θ. |
| Principle of moments | For balance, the clockwise moments about a pivot equal the anticlockwise moments. |
| Centre of gravity | The point where an object's whole weight seems to act. It must stay above the base for the object to stand. |
| Gear ratio | Teeth on the driven gear ÷ teeth on the driving gear: it multiplies torque and divides speed. |
| Power = τω | For anything that turns, power is torque × angular speed in radians per second. |
| Precession | The slow swing of a spinning object's axis when a torque acts at right angles to its spin. |
From the steelyard in a Greek market to the torque figure on a car's spec sheet: how people learned that a push is worth more further from the pivot.
- 250 BCE · The law of the lever (Archimedes, Syracuse, Sicily)
- 1500 · The 'potential lever' (Leonardo da Vinci, Milan)
- 1687 · Varignon's theorem (Pierre Varignon, Paris)
- 1765 · Torque makes things spin up (Leonhard Euler, Berlin)
- 1821 · The Prony brake measures torque (Gaspard de Prony, Paris)
- 1852 · The gyroscope gets its name (Léon Foucault, Paris)
- 1884 · The word 'torque' (James Thomson, Glasgow)
- 1888 · Motors that twist with magnetism (Galileo Ferraris and Nikola Tesla, Turin and New York)
The full story, with 20 moments, charts, people and 22 sources: glassbox.how/e/torqueclear/history. The data lives in history.json.
Made with the Glassbox studio from this box's storyboard (window.glassbox.director). Free to reuse under CC BY 4.0.
| File | What | Size |
|---|---|---|
glassbox/reel.mp4 |
Reel / Short, with captions and soundtrack | 1080×1920 |
glassbox/video.mp4 |
YouTube video, with captions and soundtrack | 1920×1080 |
glassbox/slide-1…10.jpg |
Instagram carousel | 1080×1350 |
glassbox/thumb.jpg |
YouTube thumbnail | 1280×720 |
glassbox/cover.jpg |
Share card and repo social preview | 1200×630 |
glassbox/history-reel.mp4 |
“History in 10 moments” Reel / Short | 1080×1920 |
glassbox/history-slide-*.jpg |
History carousel | 1080×1350 |
glassbox/post.json |
Post copy and schedule used by the publish kit |
This box has no accounts and no ads, and it ships its own fonts and libraries. When you run it yourself it sends nothing anywhere. On glassbox.how, the site's /bar.js also loads Glassbox's analytics: Google Analytics to count visits (it asks first in the EU, UK and Switzerland, and stays off when your browser sends Global Privacy Control or Do Not Track) and ClickTrust to detect bots.
It remembers a few things in your own browser only, and never sends them anywhere:
| Browser storage key | What it holds |
|---|---|
torqueclear.v1 |
Which chapters you have opened, your best quiz scores, and sound on or off. |
Exactly what each one sees is at glassbox.how/privacy.
- Code: MIT. Use it, change it, ship it.
- Explanations, text, images and videos (
glassbox.json,glassbox/): CC BY 4.0. Credit “Glassbox, glassbox.how/e/torqueclear”. - Third-party parts keep their own licences: three.js (MIT), Geist, Instrument Serif (SIL OFL 1.1).
- The Glassbox name and logo aren't covered by either licence. See the terms.
Found a mistake? Open an issue. Corrections happen in public.
It's plain HTML, CSS and JavaScript. No build step and no dependencies. Run locally, it contacts no other website.
python3 -m http.server 8000Three.js and the fonts ship in vendor/ and fonts/, so it also works offline.
Then open http://localhost:8000.
| File | What |
|---|---|
index.html, css/app.css |
The page and its styles |
js/app.js, js/stage.js, js/ui.js, js/kit.js |
The shared Glassbox 3D engine: chapters, 3D stage, controls, quiz, video director |
js/torque.js |
Shared parts: torque and force formatting, chart boards, straight force arrows and curled torque arrows, a hex nut, spanners, gears, seated children and people |
js/chapters/*.js |
One file per chapter: the 3D model, controls, text, key terms, quiz and video scenes |
glassbox.json |
Title, question, explainer beats, key terms, browser storage and credits shown on glassbox.how |
reel in each chapter |
The storyboard the Glassbox studio records into short videos |
glassbox/ |
The published video, slides, thumbnail and post copy |
fonts/, vendor/three/ |
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