What Makes a Car Move?

by Enzo Silvestri
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A car moves by converting the potential chemical energy of gasoline into kinetic energy at the wheels. This is done by a process of burning gasoline, which produces expansion of gas and exhaust of waste gases.


When gasoline is injected into the cylinder and mixed with air and ignited, it produces an explosion that rapidly expands the gases in the confined cylinder. Thus the four-stroke process is compression, ignition, power, exhaust.

Pistons & Crank Shaft

The piston is consequently driven downward by the expanding gases in the power stroke which exit the cylinder through an exhaust manifold in the side of the cylinder. The movement of the piston drives the crank shaft down, and this drives another piston up in its cylinder, where it repeats the process of compression, ignition, power and exhaust.

Fly Wheel & Gear Box

The spinning crank shaft turns the heavy flywheel at the rear of the engine. The flywheel is cut with teeth so the starter motor can turn it over and start the engine. The flywheel is connected directly to the gear box which enables the driver to select the ratio of the engine speed to the drive speed.

Drive Shaft

The gear box then connects to the bar of the drive shaft, which spins according to the speed of the selected gears, which in turn is connected to a split differential that allows the driving power to drive the rear axle.


The rear wheels, or in the case of front-wheel drive cars, the front wheels, are driven by the rotation of the axle. The turning wheels in turn move the car.

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