How every fact on this site was checked
113 facts. Each one is in our own words, each one has a source, and each one was checked against that source on 13 November 2026.
How we check
We read each source and wrote each fact in our own words. Our build stores the text of every source page, and for each fact it checks that the key words and figures, the “checks” in the table, really appear on the source page. If any check fails, the site does not build. Where good sources disagree, we show each version in a “Sources differ” box rather than picking one. Our own worked examples (such as the wheelbarrow’s 13.6 and the lever calculator) are labelled as our arithmetic.
Known disagreements
- How many simple machines. Six: inclined plane, lever, wedge, wheel and axle, pulley and screw (Britannica’s simple machine article; Science Trek). Five, without the inclined plane (Britannica’s pulley and wedge articles). A different six, with the block and the gear (US Navy manual), which also says physicists recognise only two principles.
- Hero’s five. Lever, pulley, wheel, wedge and screw (University of Oklahoma) or winch, lever, pulley, wedge and screw (Acta Baltica).
- Who made it six. Galileo, who added the inclined plane in Le Mecaniche (Acta Baltica); Simon Stevin worked out its mechanical advantage in 1586 (Ohio University).
- “Give me a place to stand”. Apocryphal (Britannica). Plutarch’s version: another earth to stand on. The famous lever wording: John Tzetzes, 12th century AD (Rorres, NYU).
- Door handles. A wheel and axle (US Navy manual, for a doorknob) or a lever (Science Trek).
- Who invented the screw. Archytas, the “alleged inventor”, and the water screw “usually ascribed to Archimedes” with an earlier Egyptian device (Britannica), or Mesopotamia in the first millennium BCE (Ohio University).
What we left out
- Popular claims we could not find in a reliable source, such as exact dates for the first wheel or the first pulley, are left out or given as each source words them.
- The experiments are our own classroom-style activities. Their “why” is sourced; the method is ours.
- Wordings of the Archimedes quote vary between translations; we quote the versions on our sources and call the line “attributed”.
The log
| # | Fact | Source | Checks |
|---|---|---|---|
| 1 | A simple machine is a device with few or no moving parts that changes the size or direction of a force so that a job gets done. | Encyclopaedia Britannica: Simple machine | 2 passed |
| 2 | Britannica lists six simple machines: the inclined plane, the lever, the wedge, the wheel and axle, the pulley and the screw. | Encyclopaedia Britannica: Simple machine | 1 passed |
| 3 | Britannica’s own articles on the pulley and the wedge call each of them one of “the five simple machines”, a list without the inclined plane. | Encyclopaedia Britannica: Pulley | 2 passed |
| 4 | A US Navy training manual also counts six, but a different six: the lever, the block, the wheel and axle, the inclined plane, the screw and the gear. | US Navy, Basic Machines and How They Work, ch. 1: Levers | 1 passed |
| 5 | The same manual adds that physicists recognise only two basic principles in machines: the lever and the inclined plane. | US Navy, Basic Machines and How They Work, ch. 1: Levers | 1 passed |
| 6 | In that view the wedge and the screw both work on the principle of the inclined plane. | US Navy, Basic Machines and How They Work, ch. 1: Levers | 1 passed |
| 7 | Science Trek, from Idaho Public Television, gives the familiar six: lever, wheel and axle, inclined plane, wedge, pulley and screw. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 8 | The word “machine” comes from a Greek word meaning “to help make things easier”. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |
| 9 | Simple machines can be combined into compound machines, and many everyday tools are compound machines. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 10 | The six simple machines were classified during the Renaissance. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 2 passed |
| 11 | Mechanical advantage is how many times a machine multiplies the force you put in: the output force divided by the input force. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 2 passed |
| 12 | The theoretical mechanical advantage assumes no friction; in practice friction makes the actual mechanical advantage smaller. | Encyclopaedia Britannica: Mechanical advantage | 2 passed |
| 13 | Machines multiply force at the expense of distance: you push with less force, but over a longer distance. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |
| 14 | A machine cannot do more work than the energy put into it, so energy is still conserved. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |
| 15 | A US Navy manual puts it this way: a machine lets you gain force, but only at the expense of speed. | US Navy, Basic Machines and How They Work, ch. 1: Levers | 1 passed |
| 16 | In physics, work is force multiplied by the distance moved in the direction of the force: W = fd. | Encyclopaedia Britannica: Work (physics) | 1 passed |
| 17 | Work is measured in joules. One joule is the work done by a force of one newton moving something one metre. | Encyclopaedia Britannica: Work (physics) | 1 passed |
| 18 | Holding a heavy object still, however tiring, does no work in the physics sense. | Encyclopaedia Britannica: Work (physics) | 1 passed |
| 19 | Push on a brick wall until you sweat and, unless it moves, you have done no work; nudge a computer mouse and you have. | Science Trek (Idaho Public Television): Simple machines | 2 passed |
| 20 | A force of 10 newtons that moves something 3 metres does 30 joules of work. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 21 | Ignoring friction, the work you put into a machine equals the work you get out. | US Navy, Basic Machines and How They Work, ch. 7: Work | 1 passed |
| 22 | A lever is a bar or board that rests on a support called a fulcrum. | Encyclopaedia Britannica: Simple machine | 1 passed |
| 23 | OpenStax describes it as a rigid bar pivoted at a fixed place called the fulcrum. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |
| 24 | All early people used the lever in some form, for moving heavy stones or as digging sticks. | Encyclopaedia Britannica: Simple machine | 2 passed |
| 25 | The shadoof is a long lever with a water container on the short arm and counterweights on the long arm; it is said to have been used in Egypt and India as early as 1500 BCE. | Encyclopaedia Britannica: Simple machine | 3 passed |
| 26 | With a shadoof, a person could lift several times their own weight by pulling down on the long arm. | Encyclopaedia Britannica: Simple machine | 1 passed |
| 27 | A balance beam for weighing, a bar pivoted at its centre, was probably used in Egypt in about 5000 BC, says Britannica. | Encyclopaedia Britannica: Lever | 1 passed |
| 28 | If the crowbar’s long side is five times the short side, your push is multiplied five times. | Encyclopaedia Britannica: Simple machine | 1 passed |
| 29 | A nutcracker is two levers joined at a pin: if the handle is three times as far from the pin as the nut, your squeeze is multiplied three times. | Encyclopaedia Britannica: Simple machine | 2 passed |
| 30 | Every lever has three parts to look for: the effort (your push), the fulcrum (the pivot) and the load. | BBC Bitesize: What are levers? | 3 passed |
| 31 | In a first-class lever the fulcrum is between the effort and the load, as in a seesaw or a crowbar. | BBC Bitesize: What are levers? | 3 passed |
| 32 | In a second-class lever the load is between the fulcrum and the effort: wheelbarrows, nutcrackers and some bottle openers. | BBC Bitesize: What are levers? | 1 passed |
| 33 | In a third-class lever the effort is between the fulcrum and the load: tweezers, tongs and fishing rods. | BBC Bitesize: What are levers? | 2 passed |
| 34 | The law of the lever: weights balance at distances from the fulcrum in inverse proportion to their weights. Twice the weight balances at half the distance. | Encyclopaedia Britannica: Archimedes | 1 passed |
| 35 | For any lever, the mechanical advantage equals the effort’s distance from the fulcrum divided by the load’s distance from the fulcrum. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 2 passed |
| 36 | The longer the handle on a nail puller, the more force you can exert with it. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |
| 37 | In OpenStax’s worked wheelbarrow example, the load sits 7.50 cm from the wheel’s axle and your hands 1.02 m from it. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 3 passed |
| 38 | A shovel is a lever with a mechanical advantage of less than one: it gives up force to gain speed and distance at the blade. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 2 passed |
| 39 | A claw hammer pulling a nail is a lever: a small force on the long handle gives a big pull on the nail. | US Navy, Basic Machines and How They Work, ch. 1: Levers | 1 passed |
| 40 | A pair of scissors is a double first-class lever, with the pivot screw as the fulcrum. | Illinois State University Physics: Simple machines | 1 passed |
| 41 | A nutcracker is a double second-class lever. | Illinois State University Physics: Simple machines | 1 passed |
| 42 | Your forearm is a third-class lever: the muscle pulls between the elbow and the hand. | Illinois State University Physics: Simple machines | 2 passed |
| 43 | Levers are all around us: door handles, the claws of a hammer, crowbars, light switches, bottle openers and hinges. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 44 | The closer the fulcrum is to the object being lifted, the easier it is to lift. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 45 | A wheel and axle is a wheel fixed to a shaft (the axle) so that the two turn together. | Encyclopaedia Britannica: Simple machine | 1 passed |
| 46 | In its earliest form, the wheel and axle was probably used for raising weights or buckets of water from wells. | Encyclopaedia Britannica: Wheel and axle | 1 passed |
| 47 | Its mechanical advantage is the radius of the wheel divided by the radius of the axle. | Encyclopaedia Britannica: Wheel and axle | 2 passed |
| 48 | A doorknob is a wheel and axle. Try turning the bare square shaft with your fingers once the knob is off: it is tough work. | US Navy, Basic Machines and How They Work, ch. 3: The wheel and axle | 2 passed |
| 49 | The old well windlass: an 8-inch crank turning a 2-inch drum gives a theoretical mechanical advantage of 4. | US Navy, Basic Machines and How They Work, ch. 3: The wheel and axle | 3 passed |
| 50 | A car’s front wheel is not a wheel-and-axle machine in this sense, because its axle does not turn with the wheel. | US Navy, Basic Machines and How They Work, ch. 3: The wheel and axle | 1 passed |
| 51 | OpenStax treats a crank as a lever that can turn a full circle about its pivot; cranks are usually designed to have a large mechanical advantage. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 2 passed |
| 52 | Gears are a form of the wheel and axle. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 53 | Wheels and axles are wherever things turn in a circle: fans, revolving doors, merry-go-rounds, bicycles. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 54 | The wheel and axle goes back to Mesopotamia in the fifth millennium BCE, according to an Ohio University history of mechanisms. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 1 passed |
| 55 | A pulley is a wheel that carries a rope, cord, cable, chain or belt on its rim. Pulleys with grooved rims are called sheaves. | Encyclopaedia Britannica: Pulley | 2 passed |
| 56 | Pulleys, the blocks that hold them and the rope together are called a block and tackle. | Encyclopaedia Britannica: Pulley | 1 passed |
| 57 | A single fixed pulley has a mechanical advantage of 1: it doesn’t reduce the force, it changes its direction. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |
| 58 | For a pulley system, the mechanical advantage is roughly the number of rope sections holding up the load: 2, 3, 4 and so on. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |
| 59 | Pulling down on a flagpole rope to raise the flag is a single pulley at work: down here, up there. | Science Trek (Idaho Public Television): Simple machines | 2 passed |
| 60 | Pulleys work window blinds, raise sails, lift cargo and cranes, and move lifts between floors. | Science Trek (Idaho Public Television): Simple machines | 3 passed |
| 61 | Science Trek calls the pulley a version of the wheel and axle combined with a rope or chain. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 62 | Archimedes is reported to have used compound pulleys to pull a ship onto dry land. | Encyclopaedia Britannica: Pulley | 1 passed |
| 63 | The pulley goes back to Mesopotamia in the second millennium BCE, according to the Ohio University history. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 1 passed |
| 64 | An inclined plane is a sloping surface used to raise heavy things. A ramp is the classic example. | Encyclopaedia Britannica: Inclined plane | 1 passed |
| 65 | Pushing something up a slope takes less force than lifting it straight up, if you ignore friction. | Encyclopaedia Britannica: Inclined plane | 1 passed |
| 66 | The steeper the slope, the closer the force gets to the full weight. | Encyclopaedia Britannica: Inclined plane | 1 passed |
| 67 | Without friction, the push needed is the weight times the sine of the slope’s angle: F = W sin θ. | Encyclopaedia Britannica: Inclined plane | 1 passed |
| 68 | Ramps and switchback roads use the inclined plane: a small force acting over a long distance does a large amount of work. | Encyclopaedia Britannica: Simple machine | 1 passed |
| 69 | It takes the same amount of work, but less force, to move an object up a ramp than to lift it straight up. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 70 | The Navy manual’s example: rolling a 300-pound barrel up a 9-foot plank onto a 3-foot platform takes about 100 pounds of push, a mechanical advantage of 3. | US Navy, Basic Machines and How They Work, ch. 4: The inclined plane and wedge | 3 passed |
| 71 | Stairs, escalators, ladders, wheelchair ramps and even mail chutes are versions of the ramp. | Science Trek (Idaho Public Television): Simple machines | 2 passed |
| 72 | Ramps were probably used during the construction of the Egyptian pyramids. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |
| 73 | Cattle ramps, mountain roads and gangplanks are all inclined planes. | US Navy, Basic Machines and How They Work, ch. 4: The inclined plane and wedge | 1 passed |
| 74 | A wedge tapers to a thin edge. Push it one way and it pushes sideways. | Encyclopaedia Britannica: Simple machine | 2 passed |
| 75 | Wedges split, lift and tighten, for example to fix a hammer head onto its handle. | Encyclopaedia Britannica: Wedge | 1 passed |
| 76 | Wedges were used in prehistoric times to split logs and rocks. For rocks, wooden wedges were wetted so they would swell. | Encyclopaedia Britannica: Wedge | 2 passed |
| 77 | An axe is a wedge, and so are the teeth on a saw. | Encyclopaedia Britannica: Simple machine | 1 passed |
| 78 | A wedge is really two inclined planes back to back. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 79 | Wedges also hold things in place: staples, drawing pins, nails, doorstops and shims. | Science Trek (Idaho Public Television): Simple machines | 1 passed |
| 80 | Knives, axes, needles, scissor blades and ice picks are wedges that separate. | Science Trek (Idaho Public Television): Simple machines | 3 passed |
| 81 | A zip uses two ancient tools, the wedge and the hook: the slide holds a set of wedges that push the teeth together or force them apart. | Indiana Public Media, A Moment of Science: Ode to the zipper | 3 passed |
| 82 | Scissors are a compound machine: the edges of the blades are wedges, joined to make a lever. | Science Trek (Idaho Public Television): Simple machines | 2 passed |
| 83 | In terms of how it works, a screw may be thought of as a wedge wrapped around a cylinder. | Encyclopaedia Britannica: Simple machine | 1 passed |
| 84 | Cut a right-angled triangle of paper and wind it round a pencil: the sloping edge becomes a screw thread, an inclined plane wrapped round a cylinder. | US Navy, Basic Machines and How They Work, ch. 5: The screw | 2 passed |
| 85 | A jack with a 24-inch handle and a ¼-inch thread pitch can, in theory, lift about 15 tons with a 50-pound push. | US Navy, Basic Machines and How They Work, ch. 5: The screw | 3 passed |
| 86 | Screw jacks lose a lot to friction, on purpose: without it, the weight of the load would spin the jack straight back down. | US Navy, Basic Machines and How They Work, ch. 5: The screw | 2 passed |
| 87 | Screws are in jar lids, drills, bolts, light bulbs, taps, bottle caps and ball-point pens, and a spiral staircase is a kind of screw. | Science Trek (Idaho Public Television): Simple machines | 2 passed |
| 88 | A screw pump turns a big screw shape in water to lift the water up the shaft, often for farms and irrigation. | Science Trek (Idaho Public Television): Simple machines | 2 passed |
| 89 | Archytas of Tarentum, in the 5th century BC, is the alleged inventor of the screw. | Encyclopaedia Britannica: Screw | 1 passed |
| 90 | The water screw is usually credited to Archimedes, but there is evidence of a similar device in Egypt earlier. | Encyclopaedia Britannica: Screw | 2 passed |
| 91 | The screw press was probably invented in Greece in the 1st or 2nd century BC. | Encyclopaedia Britannica: Screw | 1 passed |
| 92 | The same history traces the screw to Mesopotamia in the first millennium BCE. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 1 passed |
| 93 | Archimedes was born in about 287 BCE in Syracuse, Sicily, and died there in 212 or 211 BCE. | Encyclopaedia Britannica: Archimedes | 3 passed |
| 94 | Britannica calls the story that he said “Give me a place to stand and I will move the Earth” apocryphal: not reliably recorded. | Encyclopaedia Britannica: Archimedes | 2 passed |
| 95 | The oldest version is in Plutarch (about AD 45–120), writing some 300 years later: if there were another earth, Archimedes said, by going into it he could move this one. | Chris Rorres, Archimedes: quotations about the lever (NYU) | 2 passed |
| 96 | The famous wording, “Give me a place to stand and with a lever I will move the whole world”, is from John Tzetzes, writing in the 12th century AD. | Chris Rorres, Archimedes: quotations about the lever (NYU) | 2 passed |
| 97 | Plutarch also tells how Archimedes, holding the end of a pulley system in his hand, drew a loaded ship towards him in a straight line. | MacTutor History of Mathematics (University of St Andrews): Archimedes | 2 passed |
| 98 | The basic law of the lever was probably known to scholars before Archimedes; he gave it a mathematical proof. | Encyclopaedia Britannica: Archimedes | 2 passed |
| 99 | The later writer Pappus mentions a treatise by Archimedes On balances and levers, which is lost. | MacTutor History of Mathematics (University of St Andrews): Archimedes | 1 passed |
| 100 | Archimedes studied three machines: the lever, the pulley and the screw. | Pisano and Bussotti, Acta Baltica Historiae et Philosophiae Scientiarum (PDF) | 1 passed |
| 101 | The Greek engineer Hero of Alexandria described five simple machines: the lever, the pulley, the wheel, the wedge and the screw. | University of Oklahoma Libraries, Galileo’s World: Mechanics | 1 passed |
| 102 | Another history lists Hero’s five as the winch, lever, pulley, wedge and screw. | Pisano and Bussotti, Acta Baltica Historiae et Philosophiae Scientiarum (PDF) | 1 passed |
| 103 | The ancient Greeks’ understanding of simple machines was limited to statics, forces in balance, and did not include the idea of work. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 1 passed |
| 104 | In 1577 Guidobaldo del Monte showed that all five of Hero’s machines could be worked out from the principle of the lever. | University of Oklahoma Libraries, Galileo’s World: Mechanics | 2 passed |
| 105 | Galileo, in Le Mecaniche, added the inclined plane, so the number of simple machines became six. | Pisano and Bussotti, Acta Baltica Historiae et Philosophiae Scientiarum (PDF) | 1 passed |
| 106 | In 1586 the Flemish mathematician Simon Stevin worked out the mechanical advantage of the inclined plane. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 3 passed |
| 107 | Stevin (1548–1620) published his triangle of forces in De Beghinselen der Weeghconst (1586), the start of a new kind of statics. | Encyclopaedia Britannica: Simon Stevin | 2 passed |
| 108 | In Le Meccaniche, around 1600, Galileo was the first to show that simple machines do not create energy, only transform it. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 2 passed |
| 109 | Guidobaldo del Monte was one of Galileo’s patrons; Galileo taught at Padua from 1592 to 1610. | Encyclopaedia Britannica: Galileo | 2 passed |
| 110 | The lever goes back to the Near East in the fifth millennium BCE, according to the Ohio University history. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 1 passed |
| 111 | The same history calls the wedge ancient (think stone hand axes) and the ramp prehistoric, used to move heavy masses. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 2 passed |
| 112 | It credits Archimedes, in the third century BCE, with first developing the idea of mechanical advantage. | Ohio University, R. L. Williams: History of mechanisms (PDF) | 1 passed |
| 113 | Machines do not cheat physics: they multiply force but cannot do more work than you put in. | OpenStax College Physics 2e (Rice University), 9.5 Simple machines | 1 passed |