Cars, Trains, Planes & Ships
Every vehicle solves the same few problems: turning stored energy into motion, controlling that motion safely, and dealing with friction, air and water along the way.
These explainers open up cars, bikes, trains, planes and ships one part at a time, from the spark plug and the differential to air traffic control and the plane's black box.
Start here
How does a car engine work?
A petrol car engine works by burning fuel inside cylinders in tiny, rapid explosions. Each explosion pushes a piston, and those pistons turn a crankshaft that ultimately spins the wheels — repeating the four-stroke cycle thousands of times a minute.
How does a combustion engine work?
A combustion engine works by burning a fuel-air mixture inside cylinders to create rapidly expanding gas. That expansion pushes pistons, and a crankshaft converts their up-and-down motion into the rotation that turns the wheels — repeating in a four-stroke cycle many times a second.
How do car brakes work?
Car brakes slow a moving vehicle by converting its kinetic energy into heat through friction. When you press the pedal, hydraulic fluid transmits force to brake pads or shoes, which clamp onto spinning metal surfaces and bring the wheels to a stop.
Every explainer in this guide · 53
How does a car clutch work?
A car clutch connects the engine to the gearbox by pressing two spinning plates together, allowing power to flow smoothly. Pressing the clutch pedal separates the plates, interrupting power so gears can change without grinding.
How does a gearbox work?
A gearbox uses different-sized toothed wheels to change the speed and turning force (torque) coming from a power source. By engaging different pairs of gears, it can make an output turn faster with less force or slower with more force, while keeping the same power.
How does an electric car work?
An electric car works by storing energy in a large battery and using it to spin an electric motor that turns the wheels — no engine, fuel, or exhaust. Pressing the accelerator simply sends more electricity to the motor.
How does a self-driving car work?
A self-driving car works by using sensors to see its surroundings, software to decide what to do, and motors to steer, accelerate, and brake. Cameras, radar, and laser scanners build a live 3D map, and AI uses it to drive without a human.
How do airplanes fly?
Airplanes fly by balancing four forces: lift, weight, thrust, and drag. The wings are shaped so air moving over them generates lift — an upward force that overcomes the plane's weight — while engines provide thrust to push the plane forward fast enough for the wings to work.
How does a jet engine work?
A jet engine works by sucking in air, compressing it, mixing it with fuel and burning it, then blasting the hot exhaust out the back. That high-speed jet of gas pushes the engine — and the plane — forward, following Newton's third law.
How does a helicopter fly?
A helicopter flies by spinning long rotor blades that act like fast-moving wings, generating lift as they cut through the air. By tilting the angle of the blades, the pilot controls whether it rises, hovers, or moves in any direction.
How does a ship float?
A ship floats because its hull is shaped to push aside a large volume of water, and the upward buoyant force from the displaced water equals the ship's weight. As long as the ship weighs less than the water it displaces, it stays afloat.
How does a submarine work?
A submarine works by changing its weight to dive and surface, using tanks that fill with water or air. To dive, it floods ballast tanks with seawater to become heavier; to surface, it blows the water out with compressed air to become lighter.
How does a sailboat sail into the wind?
A sailboat sails into the wind by pointing its bow about 45 degrees off the wind direction and using the sails as airfoils to generate lift, which pulls the boat forward. The keel or centerboard prevents sideways drift, so the forward component of the lift moves the boat ahead.
How do bicycle gears work?
Bicycle gears change the ratio between how fast you pedal and how fast the rear wheel turns. By shifting the chain between differently sized front and rear sprockets, you trade pedal effort for speed or climbing ease.
How does an electric train work?
An electric train works by collecting electricity from an overhead wire or a third rail and feeding it to electric traction motors that turn the wheels. Onboard electronics convert the supply into the voltage and frequency the motors need, and the current returns to the power station through the running rails.
How does a maglev train work?
A maglev train works by using powerful magnets to lift the train a few millimetres or centimetres above its guideway and a moving magnetic field to pull it forward. With no wheels touching rails at speed, there is no rolling friction, so maglevs can travel smoothly at well over 400 km/h.
How do railway signals work?
Railway signals work by dividing the track into sections called blocks and allowing only one train into each block at a time. Detectors sense where trains are, and an interlocking system sets each signal's colour so drivers know whether the track ahead is clear, restricted or occupied.
How does a hybrid car work?
A hybrid car works by combining a petrol engine with one or more electric motors and a battery, switching between them or using both together. The battery is recharged by the engine and by regenerative braking, so the car burns less fuel, especially in stop-start city traffic.
How does a turbocharger work?
A turbocharger works by using hot exhaust gas to spin a turbine, which drives a compressor that forces extra air into the engine. More air allows more fuel to be burned in each cycle, so a smaller engine can produce the power of a much larger one.
How does a car battery work?
A car battery works by turning chemical energy into electricity through reactions between lead plates and sulfuric acid inside six connected cells. It delivers a large burst of current to crank the starter motor, then the alternator recharges it by driving those reactions backwards while the engine runs.
How does an alternator work?
An alternator works by spinning an electromagnet inside fixed coils of wire, which induces an alternating current through electromagnetic induction. Diodes convert that current to direct current, and a voltage regulator keeps the output steady so it can recharge the battery and run the car's electrical systems.
How does a spark plug work?
A spark plug works by creating a high-voltage electric spark across a small gap inside the cylinder, igniting the compressed fuel-air mixture at precisely the right moment. The ignition coil boosts the car's 12-volt supply to tens of thousands of volts so current can jump that gap.
How does fuel injection work?
Fuel injection works by spraying a precisely measured amount of pressurised fuel into the engine as a fine mist, timed by an electronic control unit. Sensors tell the computer how much air is entering and how the engine is running, so it can match fuel to air for clean, efficient combustion.
How does a car radiator work?
A car radiator works by passing hot coolant from the engine through thin tubes surrounded by metal fins, where passing air carries the heat away. The cooled liquid then flows back to the engine to absorb more heat, keeping the engine at a steady operating temperature.
How does power steering work?
Power steering works by adding force from a hydraulic pump or an electric motor to the effort the driver puts into the steering wheel. A sensor or valve detects how hard the driver is turning and supplies matching assistance, making it easy to steer at parking speeds.
How does an automatic transmission work?
An automatic transmission changes gear by itself, using a fluid coupling called a torque converter and sets of planetary gears that clutches and brakes lock in different combinations. A control unit reads road speed and accelerator position, then picks the ratio and shifts without the driver touching a clutch pedal.
How does a car differential work?
A car differential is a gear set on the driven axle that lets the left and right wheels turn at different speeds while both still receive engine power. It is needed because the outer wheel in a corner travels a longer path than the inner wheel in the same time.
How do shock absorbers work?
Shock absorbers stop a car bouncing on its springs by forcing oil through small valves in a piston, which turns the energy of each bounce into heat. The springs carry the car's weight and soak up bumps, while the shock absorbers damp the up-and-down motion that follows.
How do car tires grip the road?
Car tires grip the road through friction in a small contact patch, where soft rubber briefly sticks to the surface and deforms around its tiny bumps. That grip lets the tire push the car forward, slow it down and turn it, while tread grooves clear water so rubber stays touching the road.
How do parking sensors work?
Parking sensors work like a bat's echolocation, sending ultrasonic sound pulses from the bumper and timing how long the echoes take to bounce back. A control unit converts that time into distance and warns the driver with beeps that speed up as the car closes in on an obstacle.
How does a car key fob work?
A car key fob is a small battery-powered radio transmitter that sends a coded signal to a receiver in the car when you press a button. Each press uses a new rolling code generated from a shared secret, so the car accepts it but rejects a recording of an old signal.
How do seatbelts work?
Seatbelts work by locking in a crash and holding the body to the seat, so it slows with the car instead of flying forward into the dashboard or windscreen. The belt spreads stopping force across the strong bones of the pelvis, chest and shoulder, while pretensioners and load limiters fine-tune that force.
How do crumple zones work?
Crumple zones are the front and rear sections of a car designed to fold up in a controlled way during a collision, absorbing energy and lengthening the time the car takes to stop. Spreading the stop over more time lowers the forces reaching the people inside a rigid passenger cell.
How does a catalytic converter work?
A catalytic converter cleans car exhaust by passing it over a honeycomb coated with precious metals that speed up chemical reactions without being used up. Toxic carbon monoxide, unburned fuel and nitrogen oxides are turned into carbon dioxide, water vapour and nitrogen before the gas leaves the tailpipe.
How does EV charging work?
EV charging works by pushing electric current into a car's lithium-ion battery, with a battery management system controlling how fast it flows. At home, AC from the grid passes through a charger built into the car, while DC fast chargers convert power in the station and feed the battery directly.
How does regenerative braking work?
Regenerative braking slows an electric or hybrid vehicle by running its traction motor as a generator, turning the vehicle's motion into electricity that recharges the battery. The resistance created by generating that current provides the braking force, recovering energy that friction brakes would waste as heat.
How does an electric bike work?
An electric bike works by adding power from a battery-driven motor to the rider's own pedalling, with a controller deciding how much help to give. Sensors detect the rider's pedalling, and the assistance fades out at a legal speed limit, such as 25 km/h in India and the EU.
How does a diesel engine work?
A diesel engine burns fuel by squeezing air so hard that it becomes hot enough to ignite fuel sprayed into the cylinder, with no spark plug involved. The expanding burning gas pushes a piston down, and the crankshaft turns that push into the rotation that drives a vehicle or machine.
How does a steam engine work?
A steam engine burns fuel to boil water, and the high-pressure steam pushes a piston back and forth inside a cylinder. A connecting rod and crank turn that straight-line push into the rotation that drives wheels, pumps or machinery, while valves keep feeding fresh steam to alternate sides.
How do traffic lights work?
Traffic lights work by switching red, amber and green lamps in a timed sequence set by a controller box at the junction, so conflicting streams of vehicles take turns. Many controllers also use road sensors, cameras or push buttons to lengthen or skip phases based on the traffic actually waiting.
How does FASTag work?
FASTag works by sticking a radio-frequency identification (RFID) tag to a vehicle's windscreen, which a reader at an Indian toll plaza scans as the vehicle approaches. The tag's ID is linked to a prepaid wallet or bank account, so the toll is deducted electronically and the barrier lifts without cash.
How does a CNG car work?
A CNG car works by storing natural gas, mostly methane, in a strong tank at about 200 bar and feeding it through a pressure regulator into the engine, where spark plugs ignite it like petrol. Most are bi-fuel cars that can switch between CNG and a petrol tank.
How does autopilot work on a plane?
Autopilot on a plane works by having a computer compare the aircraft's actual heading, altitude and speed with the targets the pilots set, then moving the control surfaces to correct any difference. Pilots choose the modes, monitor every change and can disconnect it instantly with a button.
How does air traffic control work?
Air traffic control works by dividing the sky and airport surface into zones, each watched by controllers who use radar and radio to keep aircraft safely apart. Controllers issue clearances for routes, altitudes and runways, then hand each flight to the next zone as it travels.
How does a plane's black box work?
A plane's black box is actually two crash-protected recorders: a flight data recorder that logs instrument readings and a cockpit voice recorder that captures crew audio. Both store data on solid-state memory inside armoured, insulated cases, and investigators read them after an accident to reconstruct what happened.
How does a glider fly?
A glider flies by trading height for forward speed: gravity pulls it gently downhill through the air, and the airflow over its long wings creates lift that keeps the descent shallow. To stay up for hours, pilots find rising air, such as thermals or wind deflected by ridges, that climbs faster than the glider sinks.
How does a hovercraft work?
A hovercraft works by blowing air beneath its hull with a large fan, trapping it inside a flexible rubber skirt so the craft rides on a cushion of pressurised air. Separate propellers push it forward and rudders steer, letting it cross water, mud, sand and ice with very little friction.
How does a canal lock work?
A canal lock works by moving boats between two water levels inside a watertight chamber with gates at each end. Opening valves lets water flow in from the higher side or out to the lower side, so the boat rises or falls with the water until it matches the level ahead.
How does a propeller work?
A propeller works by spinning several twisted blades, each shaped like a small wing, so they push air or water backward. By Newton's third law, accelerating that fluid rearward creates an equal forward force called thrust, which moves an aircraft, ship or drone through its surroundings.
How does a lighthouse work?
A lighthouse works by focusing a bright lamp through a lens into a powerful horizontal beam that sailors can see many kilometres out at sea. Each lighthouse flashes in its own timed pattern, marked on nautical charts, so navigators can identify which light they are seeing and fix their position.
How does a cable car work?
A cable car works by hanging cabins from steel ropes strung between towers and pulling them along with a moving haul rope driven by a large electric motor in one station. A wheel at the other end keeps the loop tight, so cabins can climb steep slopes, valleys and rivers without roads.
How does airplane cabin pressure work?
Airplane cabin pressure works by pumping compressed air into the sealed fuselage while an outflow valve controls how fast it escapes, keeping the cabin far denser than the thin air outside. At cruise the cabin is typically held at the pressure found about 1,800 to 2,400 metres above sea level.
How do anti-lock brakes (ABS) work?
Anti-lock brakes stop a wheel from locking during hard braking by rapidly releasing and reapplying brake pressure whenever a sensor detects that wheel slowing too fast. Keeping each tire rolling just short of a skid preserves grip, so the car stays steerable even under hard braking.
Key ideas behind them
What is inertia?
Inertia is an object's resistance to changes in its motion. A still object stays still, and a moving object keeps moving, unless a force acts on it. It's the heart of Newton's first law — and why you lurch forward when a car suddenly brakes.
What is momentum in physics?
Momentum is a measure of how much motion an object has — it depends on both its mass and its velocity. A heavy, fast object has lots of momentum and is hard to stop. In a closed system, total momentum is always conserved.
What is friction?
Friction is the force that resists motion when two surfaces rub against each other. It's why a sliding book slows and stops, why we can walk without slipping, and why rubbing your hands makes heat. No surface is perfectly smooth, so friction is everywhere.
What is acceleration?
Acceleration is how quickly an object's velocity changes — speeding up, slowing down, or changing direction. When you press a car's accelerator, you increase its velocity; braking is acceleration in the opposite direction (deceleration).
What is velocity?
Velocity is the speed of an object in a specific direction. Unlike speed, which is just a number, velocity tells you both how fast something moves and which way it's going — for example, 50 km/h heading east.
What are Newton's laws of motion?
Newton's three laws of motion describe how objects move and respond to forces. Together they explain everything from a rolling ball to a launching rocket, and form the foundation of classical mechanics.
What is centripetal force?
Centripetal force is the inward force that keeps an object moving in a circle. Without it, the object would fly off in a straight line. It's what holds a car on a curved road, a ball on a string, and the Moon in orbit around Earth.
What is buoyancy?
Buoyancy is the upward force a fluid exerts on an object placed in it. If that force is greater than the object's weight, it floats; if less, it sinks. It's why ships float and why you feel lighter in water.
हिंदी में पढ़ें: सेल्फ-ड्राइविंग कार कैसे काम करती है? · इलेक्ट्रिक ट्रेन कैसे चलती है? · FASTag कैसे काम करता है? · CNG कार कैसे चलती है?
Frequently asked questions
What is the difference between a petrol and a diesel engine?
A petrol engine uses a spark plug to ignite a fuel–air mixture. A diesel engine has no spark plugs: it squeezes air so hard that it becomes hot enough to ignite the diesel as it is sprayed in.
Why do planes fly so high?
Air is thinner at cruising altitude, so there is less drag and jet engines burn less fuel per kilometre. Flying high also keeps planes above most weather.
How do electric cars differ from petrol cars?
An electric car stores energy in a battery and drives the wheels with an electric motor, so it has no fuel tank, exhaust or multi-speed gearbox, and it can recover energy when braking.