How a car works

Inside the engine, petrol burns in tiny explosions. Each explosion pushes a piston down. The piston turns a crank, and the crank spins the wheels. Use the slider to run it slowly, or press Next stroke to see one step at a time.

A pump sends petrol from the tank to the engine. The injector sprays it as a fine mist. A coil makes a big spark from the small battery. Press the accelerator and both get faster.

A running engine gets very hot. Water (coolant) flows around it, picks up the heat, and carries it to the radiator at the front. Air and a fan cool it down. Try breaking the fan in a traffic jam and watch the temperature.

Drive it like a real car: clutch to 100%, drag the stick into 1st, a little accelerator, then slowly slide the clutch back to 0%. Let it out too fast and you will stall. Rev too hard and you must change up.

Torque is how hard something is being twisted. A long spanner gives more torque than a short one for the same push. Gears multiply the engine's torque so a small engine can move a heavy car.

Steer the car round a real track with the wheel. When the car turns, the outside wheel has further to go, so the differential lets it spin faster while giving both wheels the same turning push (torque). The circuit is twisty, and you can leave the road, but the grass is slow.

Tyres grip the road with friction, but only up to a limit. On this skid pad, hold the wheel turned and raise the speed until the tyres let go. You'll see the car point one way and slide another.

Drag the steering wheel round. A small gear moves a long toothed bar sideways, and the bar pushes the front wheels to point left or right.

Springs let the wheels go up and down over bumps while the car body stays steady. Shock absorbers stop the springs from bouncing again and again. Drive over speed breakers and watch the chai.

Slide the brake up. Liquid pushes brake pads against the spinning disc. Rubbing (friction) slows the wheel and makes heat. Try a wet road with ABS on and off.

Burning petrol makes some poisonous gases. A box called the catalytic converter turns most of them into safer gases, but only when it is hot.

An electric car has no petrol engine. A big battery powers an electric motor that spins the wheels. When you brake, the motor even puts some energy back into the battery.