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The six simple machines

Lever, wheel and axle, pulley, ramp, wedge and screw — the six shapes that trade distance for strength, the bargain behind mechanical advantage, and where all six are hiding in your kitchen.

15 steps3 min readNarrated with a studio voice
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The six simple machinesall obeyincludesincludesincludesincludesincludesincludespivots onis two ofis a wrappedmeasured asgivesgivesgivesreduced bycombine intocombine intofor exampleare mostlyhideshidesA key idea or topic — the main building block of the mapSimple machinesA concrete example of a concept — drawn as an ovalWork is force times distanceA key idea or topic — the main building block of the mapThe leverA narrower idea branching off a conceptFulcrum, effort and loadA key idea or topic — the main building block of the mapThe wheel and axleA key idea or topic — the main building block of the mapThe pulleyA key idea or topic — the main building block of the mapThe inclined planeA key idea or topic — the main building block of the mapThe wedgeA key idea or topic — the main building block of the mapThe screwA concrete example of a concept — drawn as an ovalMechanical advantageA concrete example of a concept — drawn as an ovalFriction takes its cutA key idea or topic — the main building block of the mapCompound machinesA narrower idea branching off a conceptA bicycleA concrete example of a concept — drawn as an ovalMachines inside youA concrete example of a concept — drawn as an ovalSix machines in one kitchen
The six simple machines — the complete diagram. Press Present to watch it build itself.
The six simple machines — Simple machines
Step 1 of 15

Simple machines

A simple machine has no motor, no fuel and no moving parts you could call clever. It is just a shape that changes how a force works, and there are only six of them. Every crane, engine and bicycle ever built is those six in combination.

The six simple machines — Work is force times distance
Step 2 of 15

Work is force times distance

Here is the catch nobody mentions. Work equals force multiplied by distance, and no machine can create work out of nothing. If a ramp halves the push you need, it makes you push twice as far. You trade distance for strength, never for less effort overall.

The six simple machines — The lever
Step 3 of 15

The lever

A lever is a stiff bar that turns on a pivot. Push down far from the pivot and you lift a heavy load close to it. Archimedes was not joking when he said that, given a long enough lever and somewhere to stand, he could move the Earth.

The six simple machines — Fulcrum, effort and load
Step 4 of 15

Fulcrum, effort and load

Where you put the pivot changes everything. A seesaw has the pivot in the middle, a wheelbarrow puts the load in the middle, and your own forearm puts the effort in the middle, which costs you strength but buys your hand a lot of speed.

The six simple machines — The wheel and axle
Step 5 of 15

The wheel and axle

A wheel and axle is really a lever that keeps going round. A wide steering wheel turning a thin shaft multiplies your grip many times over, and because a rolling wheel never scrapes along the ground, it wipes out most of the friction of dragging something.

The six simple machines — The pulley
Step 6 of 15

The pulley

A pulley changes the direction of your pull, so you can haul downwards instead of lifting upwards. Add a second moving pulley and the rope carries half the load on each side. A crane block threaded with six lines lets a motor lift six times what it should.

The six simple machines — The inclined plane
Step 7 of 15

The inclined plane

A ramp is a machine even though nothing inside it moves. Lifting a barrel two metres straight up is brutal. Rolling it up a ten metre slope to exactly the same height needs about a fifth of the force, and every wheelchair ramp is that bargain poured in concrete.

The six simple machines — The wedge
Step 8 of 15

The wedge

A wedge is an inclined plane you drive into things rather than climb. It turns a push forwards into an enormous shove sideways. Your front teeth, an axe head, a nail and a zip are all wedges, and the longer and thinner the wedge, the less force it demands.

The six simple machines — The screw
Step 9 of 15

The screw

Unwrap the thread of a screw and you get a long thin ramp wound round a cylinder. That is why many turns move a screw forward barely at all, and why a car jack that lifts a whole tonne can be worked comfortably with two fingers.

The six simple machines — Mechanical advantage
Step 10 of 15

Mechanical advantage

Mechanical advantage is simply the load divided by your effort. A crowbar might give you ten, meaning ten kilograms lift for every kilogram you push down. Work that number out and you know in advance exactly how much easier a machine is going to make your day.

The six simple machines — Friction takes its cut
Step 11 of 15

Friction takes its cut

No real machine reaches its promised number. Friction and bending steal part of every push, often five to twenty in every hundred, and that stolen energy leaves as heat. It is why a rope over a rusty pulley feels stiff and why machines grow warm when they work hard.

The six simple machines — Compound machines
Step 12 of 15

Compound machines

Bolt simple machines together and you get a compound machine. Scissors are two levers carrying two wedges. Nail clippers stack three levers in a row. Nothing new is ever invented at this point, the same six ideas just get attached to one another.

The six simple machines — A bicycle
Step 13 of 15

A bicycle

A bicycle is the champion of the lot. Levers in the pedals and brakes, wheels and axles at both ends, screws holding the seat, and wedge shaped teeth on the gears. It carries a person further on a bowl of porridge than any animal or machine on Earth.

The six simple machines — Machines inside you
Step 14 of 15

Machines inside you

Your skeleton is a box of levers. Elbow, jaw and ankle each pivot on a joint while a muscle pulls close to that pivot, trading strength for speed. Your calf muscle heaves with several times your body weight just so your toes can flick you forward at a run.

The six simple machines — Six machines in one kitchen
Step 15 of 15

Six machines in one kitchen

Look around a kitchen and count them off. Knife and grater are wedges, jar lids and bottle tops are screws, a door handle is a wheel and axle, a bottle opener is a lever, a blind cord runs over a pulley, and a chopping board tilted to pour is a ramp.

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