https://gearsplained.com/how-does-a-zipper-work/https://gearsplained.com/posters/zipper.jpg?v=dae645e5ddHow does a zipper work?A zipper is two rows of identical teeth, offset by half a tooth. The slider's Y-shaped channel steers the rows together at a slight angle, so the bump on each tooth drops into the hollow under the tooth opposite and the two rows lock into one chain. Pull the slider back and a small wedge at the top of the channel pries the teeth apart again.https://gearsplained.com/videos/how-a-zipper-works.mp4?v=aba3d9bd1e242026-10-19T00:00:00Zyeshttps://gearsplained.com/how-does-a-pin-tumbler-lock-work/https://gearsplained.com/posters/lock.jpg?v=c05bfcc8a5How does a pin tumbler lock work?Inside the lock, a cylinder called the plug is held still by stacks of spring-loaded pins that reach across the thin gap between the plug and the housing, the shear line. The cuts on the right key lift each stack to exactly the height where the split between its two pins sits on that line. When every gap lines up, nothing bridges the shear line, so the plug can turn and takes the cam that moves the bolt with it.https://gearsplained.com/videos/how-a-pin-tumbler-lock-works.mp4?v=08f010af7c242026-10-19T00:00:00Zyeshttps://gearsplained.com/how-does-a-toilet-flush/https://gearsplained.com/posters/toilet.jpg?v=00ef920f4bHow does a toilet flush?When you press the button, the flush valve in the cistern opens and the stored water rushes down into the bowl faster than the trap can carry it away. The bowl fills past the top of the trap, and the water spills through it and takes the contents with it. Then the valve closes, the fill valve refills the cistern until a float shuts it off, and the water left in the trap seals the pipe against sewer gas.https://gearsplained.com/videos/how-a-toilet-flushes.mp4?v=5ea369dde6222026-10-19T00:00:00Zyeshttps://gearsplained.com/how-does-a-speedometer-work/https://gearsplained.com/posters/speedometer.jpg?v=9c2bcd25beHow does a speedometer work?In a classic speedometer, a cable from the gearbox spins a magnet inside a thin aluminium cup. The moving magnet sets up eddy currents in the aluminium, and they drag the cup along in the same direction. A small hairspring pulls the cup back. The faster the magnet spins, the harder the drag, so the cup and the needle on it turn further before the spring balances them. Modern cars count pulses from a sensor at the wheel instead.https://gearsplained.com/videos/how-a-speedometer-works.mp4?v=77e91852f8252026-10-20T00:00:00Zyeshttps://gearsplained.com/how-does-a-piano-key-work/https://gearsplained.com/posters/piano.jpg?v=a3aff92d63How does a piano key make a sound?When you press a key, it tips like a seesaw and pushes up a part called the jack, which lifts the hammer. Just before the hammer reaches the string, the jack slips out from under it. The hammer flies the last bit on its own, hits the string and bounces straight back, so the string can ring. At the same time, the far end of the key lifts the damper off the string. When you let go, the damper drops back and the sound stops.https://gearsplained.com/videos/how-a-piano-key-works.mp4?v=112437becd242026-10-20T00:00:00Zyeshttps://gearsplained.com/how-does-a-quartz-watch-keep-time/https://gearsplained.com/posters/quartz.jpg?v=ea828c26ccHow does a quartz watch keep time?A quartz watch has five steps. A tiny quartz tuning fork rings 32,768 times a second. A simple step that halves the beat is repeated 15 times, which turns that into exactly one beat per second. Each beat sends current through a coil, which flips a small magnet half a turn, and gears move the seconds hand one step.https://gearsplained.com/videos/how-a-quartz-watch-keeps-time.mp4?v=efc04bbf3d442026-10-20T00:00:00Zyeshttps://gearsplained.com/how-does-a-sewing-machine-make-a-stitch/https://gearsplained.com/posters/sewing.jpg?v=736e0b82c7How does a sewing machine make a stitch?A sewing machine uses two threads: one from the spool on top, and one from a small bobbin under the fabric. The needle pushes the top thread down through the fabric. As it starts back up, a loop opens, and a spinning hook catches it and carries it all the way around the bobbin. When the loop is pulled tight, the top thread has wrapped around the bobbin thread, and the two lock together inside the fabric. Then the fabric moves on and it happens again.https://gearsplained.com/videos/how-a-sewing-machine-makes-a-stitch.mp4?v=66f64b0cf4572026-10-21T00:00:00Zyeshttps://gearsplained.com/how-does-a-helicopter-steer/https://gearsplained.com/posters/helicopter.jpg?v=2670bb41dbHow does a helicopter steer?A helicopter's rotor blades are long, thin wings. The engine keeps them spinning at an almost steady speed, and each blade pushes air down, so the air pushes it up. To climb, the pilot tilts every blade a little more at the same time: more lift. To move forward, a plate under the blades makes each blade tilt a little more on one side of the circle and a little less on the other, so the whole spinning disc leans and pulls the helicopter that way. A small rotor on the tail pushes sideways to stop the body from spinning the opposite way to the big rotor.https://gearsplained.com/videos/how-a-helicopter-steers.mp4?v=276ed42c1a562026-10-22T00:00:00Zyeshttps://gearsplained.com/how-does-a-microwave-heat-food/https://gearsplained.com/posters/microwave.jpg?v=0f45f01fcdHow does a microwave heat food?Inside the oven sits a small airless tube. A glowing hot wire in its middle gives off tiny charged specks called electrons, and two magnets bend their path into a circle. As they rush past small hollows in a copper ring, the hollows start to "ring", like blowing across a bottle, about 2450 million times a second. That makes invisible waves, which a metal channel guides into the box. The metal walls bounce them around, and the net in the door keeps them in. The waves make the water in food twist back and forth, and that jostling is heat. The plate turns because of hot and cold spots, and the outer layer heats first while the middle warms as the heat spreads inwards.https://gearsplained.com/videos/how-a-microwave-heats-food.mp4?v=3501d9fc1a722026-10-23T00:00:00Zyeshttps://gearsplained.com/how-does-a-fridge-and-heat-pump-work/https://gearsplained.com/posters/fridge-heat-pump.jpg?v=af7f3dd48fHow do a fridge and a heat pump move heat?A fridge doesn't make cold: it moves heat from inside the box to the kitchen. A closed loop of pipe holds a fluid that boils even far below freezing. A pump squeezes the gas so it gets hot, a coil on the back gives that heat to the kitchen air and the gas turns back into liquid, a tiny gap drops the pressure so the liquid boils and turns ice cold, and a cold coil inside soaks up heat from the food. A heat pump is the very same loop, with the cold coil outdoors and the hot coil inside the house.https://gearsplained.com/videos/how-a-fridge-and-heat-pump-move-heat.mp4?v=90cfbabfd8642026-10-24T00:00:00Zyeshttps://gearsplained.com/how-does-gps-know-where-you-are/https://gearsplained.com/posters/gps.jpg?v=78c3a00583How does GPS know where you are?About 30 GPS satellites circle the Earth some 20,000 km up, and each one keeps sending its position and the exact time. Your phone notes when each signal arrives. The longer a signal took, the farther away that satellite is. Each distance puts you somewhere on a circle around one satellite, and only one spot fits them all. A fourth satellite lets the phone fix its own, much less exact clock. The satellites' clocks have to be extremely exact: a millionth of a second off means about 300 metres off.https://gearsplained.com/videos/how-gps-knows-where-you-are.mp4?v=6cfadee302582026-10-25T00:00:00Zyeshttps://gearsplained.com/how-does-yeast-make-bread-rise/https://gearsplained.com/posters/yeast.jpg?v=c46c06b35dHow does yeast make bread rise?Yeast is a tiny living fungus, and one spoonful holds billions of them. In bread dough they eat sugar from the flour and give off gas, the same gas as the fizz in soda, plus a little alcohol. Kneading turns flour and water into a net of stretchy strands that traps the gas in tiny bubbles. Over an hour or two the bubbles grow and the dough rises. In the oven the heat makes the gas swell even more, the yeast dies, the alcohol boils off, and the dough sets with the bubbles frozen in place as holes.https://gearsplained.com/videos/how-yeast-makes-bread-rise.mp4?v=89f4bcc36c592026-10-26T00:00:00Zyeshttps://gearsplained.com/how-does-a-wing-create-lift/https://gearsplained.com/posters/wing.jpg?v=4e3582f5dfHow does a wing create lift?A wing is shaped and tilted so that it bends the oncoming air downward. Bending the flow creates lower pressure over the top and higher pressure underneath, and that pressure difference pushes the wing up. It's the same thing seen two ways: the wing pushes air down, and the air pushes the wing up.https://gearsplained.com/videos/how-a-wing-makes-lift.mp4?v=f7126026fe142026-10-19T00:00:00Zyeshttps://gearsplained.com/how-does-fog-form/https://gearsplained.com/posters/fog.jpg?v=97f3641958How does fog form?Fog is simply a cloud that touches the ground. Air always carries some water, spread out as an invisible gas. On a clear, calm night the ground loses its warmth up into the sky and chills the air just above it. Cold air can't hold as much water as warm air, so cooling it is like squeezing a sponge, and the extra water gathers on tiny specks of dust, salt and smoke and turns into droplets far too small to fall. Billions of them bounce light in every direction, so the air looks white and you can't see far. In the morning the sun warms the ground and the air, the droplets turn back into invisible water, and the fog fades away.https://gearsplained.com/videos/how-fog-forms.mp4?v=0724bdc8f7592026-10-27T00:00:00Zyeshttps://gearsplained.com/how-does-a-computer-count/https://gearsplained.com/posters/binary.jpg?v=2c624cfda5How does a computer count?Inside every computer are billions of tiny switches, and each one can only be off or on. Off means 0 and on means 1. To write bigger numbers, the computer lines switches up in a row, and each switch is worth twice as much as the one to its right: 1, 2, 4, 8 and so on. Add up the switches that are on and you get the number, so on-off-on-on is 8 + 2 + 1 = 11. Counting works just like a car's odometer: when a place is full it goes back to zero and passes a carry to the next place. Four switches count from 0 to 15, eight count to 255, and 32 count past four billion.https://gearsplained.com/videos/how-a-computer-counts.mp4?v=9c1607fc7d602026-10-27T00:00:00Zyeshttps://gearsplained.com/how-do-gears-work/https://gearsplained.com/posters/gears.jpg?v=9774fcdd43How do gears work?A gear is a wheel with teeth. When two gears touch, the teeth of one sit in the gaps of the other, so one can't turn without the other. The second gear always turns the opposite way. If a small gear turns a gear with twice as many teeth, the big gear turns only once for every two turns of the small one: slower, but with twice the turning force (100 Nm in becomes 200 Nm out). Swap them round and you get speed instead of force. It's just like the gears on a bike: in the easy gear you pedal fast and climb hills slowly, in the hard gear you pedal slowly and fly along on the flat.https://gearsplained.com/videos/how-do-gears-work.mp4?v=ce0fbc55d3582026-10-27T00:00:00Zyeshttps://gearsplained.com/why-do-boats-float/https://gearsplained.com/posters/buoyancy.jpg?v=0d8caf311dWhy do boats float?A boat floats when the water it pushes aside weighs as much as the boat itself. A cubic metre of water weighs 1,000 kg. Squeeze 1,000 kg of steel into a solid lump and it only takes up about 0.13 cubic metres, so it pushes aside just 130 kg of water: 130 kg holding it up, 1,000 kg pulling it down, so it sinks. Shape the same 1,000 kg into a wide, dry hull full of air and it sinks in only until it has pushed aside 1,000 kg of water, and there it floats. Let water flood in and the boat gets heavier without getting bigger, so it sinks.https://gearsplained.com/videos/why-do-boats-float.mp4?v=6e7a9cf803582026-10-28T00:00:00Zyeshttps://gearsplained.com/how-do-jet-engines-work/https://gearsplained.com/posters/jet-engines.jpg?v=5873f2d690How do jet engines work?Every jet engine does four things to air: suck, squeeze, bang, blow. Spinning blades pull air in and squeeze it into a much smaller space. Fuel burns in it non-stop, and the hot air rushes out the back so fast that the engine is shoved forward, just like a balloon you let go of. Airliners add a giant fan that pushes lots of extra air around the outside, which gives most of the push for less fuel. Propeller planes and helicopters use the same engine to spin a propeller or a rotor instead.https://gearsplained.com/videos/how-do-jet-engines-work.mp4?v=68f7e5b42a662026-10-28T00:00:00Zyeshttps://gearsplained.com/why-does-boiling-water-bubble/https://gearsplained.com/posters/boiling.jpg?v=41d776d095Why does boiling water bubble?When you heat a pot of water, the first tiny bubbles are air that was hiding in the water. Warm water can't hold as much air, so it comes out. The big bubbles of a real boil are water turned into steam. They start in tiny scratches in the pot, and at 100 °C they reach the top and escape. One spoon of water makes about 1,700 spoons' worth of steam. On a mountain, less air presses on the water, so it boils sooner: about 70 °C on top of Mount Everest. A pressure cooker does the opposite and boils at about 120 °C.https://gearsplained.com/videos/why-does-boiling-water-bubble.mp4?v=bd6bcf3b89582026-10-28T00:00:00Zyeshttps://gearsplained.com/how-does-a-car-gearbox-work/https://gearsplained.com/posters/gearbox.jpg?v=4f802de5a7How does a car gearbox work?A car engine spins fast but doesn't push very hard, so a gearbox trades speed for force, just like the gears on a bike. Inside a manual gearbox, the engine turns an input shaft, which turns a layshaft full of gears. Those gears turn a row of gears on the output shaft, but they spin loose until a sliding collar locks one of them to the shaft. In 1st gear the engine turns about 3.5 times for every turn out, so about 200 Nm becomes about 700 Nm. In 5th, about 0.8:1, the output turns faster than the engine for easy cruising. Reverse slips one small extra gear in between, which flips the direction.https://gearsplained.com/videos/how-does-a-car-gearbox-work.mp4?v=f17e5a1ce5582026-10-29T00:00:00Zyeshttps://gearsplained.com/how-does-a-car-differential-work/https://gearsplained.com/posters/differential.jpg?v=6b3878e894How does a car differential work?When a car turns, the outer wheel travels further than the inner one in the same time, so it has to spin faster. A differential makes that possible. The engine turns a big ring gear and the box it is bolted to; small spider gears inside the box let one wheel speed up exactly as much as the other slows down. The catch: an open differential always gives both wheels about the same force, so if one wheel is on ice, it just spins. A limited-slip differential (LSD) brakes the spinning wheel with clutch plates, so the wheel that grips can get several times more force.https://gearsplained.com/videos/how-does-a-car-differential-work.mp4?v=dad6603bfc582026-10-29T00:00:00Zyeshttps://gearsplained.com/how-does-a-rainbow-form/https://gearsplained.com/posters/rainbow.jpg?v=5528c75b47How does a rainbow form?A rainbow is sunlight that has been bent, split and bounced back by millions of raindrops. Light bends as it enters a round drop, and each colour bends a little differently. It bounces off the back of the drop and comes out again: red at about 42° and violet at about 40° from the point straight opposite the sun. That is why you only see a rainbow with the sun behind you and fairly low in the sky, and why everyone sees their own rainbow.https://gearsplained.com/videos/how-does-a-rainbow-form.mp4?v=d689e52bb8582026-10-29T00:00:00Zyeshttps://gearsplained.com/how-does-lightning-happen/https://gearsplained.com/posters/lightning.jpg?v=14d86ac4e5How does lightning happen?Lightning is a giant spark. Inside a storm cloud, tiny ice crystals rise and soft hail falls, and every time they bump, a little electric charge moves: the top of the cloud ends up plus, the bottom minus. When the difference gets big enough, a faint path steps down from the cloud, tall things on the ground reach up to meet it, and a huge current flashes along the path, heating the air to about 30,000 °C. The air bursts outwards, and that bang is thunder.https://gearsplained.com/videos/how-does-lightning-happen.mp4?v=905d0dfbae582026-10-29T00:00:00Zyeshttps://gearsplained.com/how-do-tides-work/https://gearsplained.com/posters/tides.jpg?v=441924f9cdHow do tides work?The Moon pulls on the whole Earth, but hardest on the side facing it and least on the far side. That stretches the oceans into two bulges, one towards the Moon and one away from it. As Earth spins, your beach passes through both bulges, so most coasts get about 2 high tides and 2 low tides a day. The Sun does the same thing about half as strongly, making extra-big tides when it lines up with the Moon and smaller ones when it doesn't.https://gearsplained.com/videos/how-do-tides-work.mp4?v=8af49214bc582026-10-29T00:00:00Zyeshttps://gearsplained.com/how-does-a-four-stroke-engine-work/https://gearsplained.com/posters/fourstroke.jpg?v=02da32989cHow does a four-stroke engine work?A car engine is a row of pistons sliding up and down in tubes. Each one repeats four jobs: suck, squeeze, bang, blow. Only the bang pushes, but it pushes hard, about 3.5 tonnes on one piston, and a crank turns that up-and-down push into the round turning that drives the wheels.https://gearsplained.com/videos/how-does-a-four-stroke-engine-work.mp4?v=fde6fd29aa582026-10-30T00:00:00Zyeshttps://gearsplained.com/how-do-car-brakes-and-abs-work/https://gearsplained.com/posters/brakes.jpg?v=5f9817d23eHow do car brakes and ABS work?Your foot only pushes with about 30 kg, but the pedal is a lever, a booster helps, and brake fluid passes the push from a small piston to a bigger one. By the time it reaches the wheel, the pads squeeze the spinning disc with roughly 2.5 tonnes, and the rubbing turns the car's motion into heat. If you brake so hard that a wheel stops turning, the tyre slides and you can't steer. ABS spots that and eases off and reapplies the brake many times a second, so the wheel keeps rolling.https://gearsplained.com/videos/how-do-car-brakes-and-abs-work.mp4?v=721aa8eac0582026-10-30T00:00:00Zyeshttps://gearsplained.com/how-does-a-turbocharger-work/https://gearsplained.com/posters/turbo.jpg?v=3a1d61e5d0How does a turbocharger work?An engine throws away a lot of hot, fast exhaust. A turbo puts a little wheel in that exhaust, and the wheel spins a second wheel on the same shaft that blows extra air into the engine. With more air in each cylinder, more fuel can burn, so a small engine can make the power of a bigger one.https://gearsplained.com/videos/how-does-a-turbocharger-work.mp4?v=7c5388085a582026-10-30T00:00:00Zyeshttps://gearsplained.com/how-does-a-hydraulic-jack-work/https://gearsplained.com/posters/jack.jpg?v=4dc805dbd1How does a hydraulic jack work?A hydraulic jack lets one hand lift a car. You pump oil with a thin piston into a cylinder under a fat piston. The oil passes the pressure on unchanged, and the fat piston has much more area, so it pushes much harder, but it moves much less.https://gearsplained.com/videos/how-does-a-hydraulic-jack-work.mp4?v=f9a0886fc1582026-10-30T00:00:00Zyeshttps://gearsplained.com/how-does-an-induction-hob-work/https://gearsplained.com/posters/induction.jpg?v=5dd7d25c9bHow does an induction hob work?An induction hob has no flame and no glowing ring. A coil under the glass makes a magnet that flips back and forth very fast, and that sets electricity swirling inside the pan's iron base. The pan heats itself from the inside, while the glass only gets warm from the hot pan.https://gearsplained.com/videos/how-does-an-induction-hob-work.mp4?v=c77fc239e9582026-10-30T00:00:00Zyeshttps://gearsplained.com/why-is-the-sky-blue/https://gearsplained.com/posters/sky.jpg?v=c1bb937b2bWhy is the sky blue and the sunset red?The sky isn't blue because of the sea or because air is "blue stuff". Air molecules bounce short (blue) light waves around much more than long (red) ones. By day that bounced blue comes at you from every direction; at sunset the light's long trip through the air strips the blue out and leaves red.https://gearsplained.com/videos/why-is-the-sky-blue.mp4?v=02cf52d67d582026-10-30T00:00:00Zyes