What are work and power?
Pull a crate at an angle, wind a bucket up a well, and watch the joules pile up under a graph. Race up the stairs at 350 watts, meet Watt's horse, lift a rice sack with a lever, pulley and ramp, read your electricity bill in kilowatt-hours, and find out why holding still makes you tired but does no work.
▶ Play with it · Read the 60-second explainer · Watch the 40-second video
- Force times distance. You do work when a force moves something along its direction: W = F × d, in joules. Pull at an angle and only F cos θ counts. On a force–distance graph, the work is the area under the line. If nothing moves, no work is done.
- Power is a rate. Power is work ÷ time, in watts. Running up 3 m of stairs in 5 s, a 60 kg student makes about 350 W. A cyclist holds 100 to 250 W. Watt's mill horse did 33,000 foot-pounds a minute: 1 hp = 745.7 W.
- Machines trade force for distance. Levers, pulleys, ramps and gears let a small force do a big job, but only by moving further. Work in = work out, minus friction. A bike chain is about 97% efficient; a petrol engine about 30%.
- Paying for work. Electricity is sold by the kilowatt-hour: 1 kWh = 3.6 MJ. A 1.5 kW AC for 6 hours a day uses 270 units a month. Food is energy too: 2,000 kcal a day is 8.4 MJ, an average of about 97 W.
- Myths and limits. Carrying a bag level does no work on it: the force is at 90° to the motion. More power doesn't mean more work, just faster work. Brakes do negative work. And holding still tires you because myosin heads keep burning ATP without moving anything.
| Term | Meaning |
|---|---|
| Work | Energy handed over by a force that moves something: force × distance moved along the force. |
| Joule (J) | The unit of work and energy: a force of 1 newton acting over 1 metre. |
| Power | How fast work is done: work ÷ time, or force × speed. |
| Watt (W) | The unit of power: one joule every second. |
| Horsepower (hp) | James Watt's unit of power: 33,000 foot-pounds per minute, 745.7 W. |
| Kilowatt-hour (kWh) | 1,000 W for one hour: 3.6 MJ. One 'unit' on an electricity bill. |
| Mechanical advantage | How many times a machine multiplies your force. It always costs the same factor in distance. |
| Efficiency | Useful work out ÷ energy in. The rest is lost, mostly as heat. |
From Archimedes' lever to the star label on your AC: how people learned that force times distance is something you can measure, sell and pay for.
- 250 BCE · The law of the lever (Archimedes, Syracuse, Sicily)
- 1600 · You can't cheat nature (Galileo Galilei, Padua, Republic of Venice)
- 1782 · One horsepower (James Watt and Matthew Boulton, Birmingham, England)
- 1829 · Travail: work gets its name (Gaspard-Gustave Coriolis, Paris, France)
- 1845 · The paddle wheel (James Prescott Joule, Manchester, England)
- 1888 · A meter for AC (Oliver B. Shallenberger, Pittsburgh, USA)
- 2006 · India's star labels (Bureau of Energy Efficiency, New Delhi, India)
The full story, with 20 moments, charts, people and 29 sources: glassbox.how/e/workclear/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 |
|---|---|
workclear.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/workclear”. - 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/chapters/*.js |
One file per chapter: the 3D model, controls, text, key terms, quiz and video scenes |
js/work.js |
Shared WorkClear parts: joule, watt and rupee formatting, power comparison data, chart boards, force arrows, a looping job timer, and the person, car, bucket, rice sack and horse models |
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/ |
Self-hosted Geist and Instrument Serif (SIL OFL 1.1) and three.js (MIT) |