3 Simple Machines Used in Cars

by Matt Koble
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Simple machines are used to make multiplying, manipulating and directing force easier. There are six widely accepted simple machines, all used in various ways in vehicles. Simple machines aren't very complex and usually have few moving parts, if any. By using simple machines together, we get machines like cars, made up of many simple machines but much too complex to be considered one.

Wheel and Axle

The wheel and axle simple machine is used in the car's axle and drive line. These machines consist of a small shaft --- an axle --- connected to a larger cylindrical shape, like a wheel. In a rear-wheel drive car, the back wheels and axle act in this fashion. Another example is the steering wheel. An easy way to illustrate the wheel and axle model's importance to the steering wheel is to compare a car with power steering to one without. The one with it likely has a much smaller steering wheel. Without power steering, turning the steering wheel requires much more force, which is easier to exert turning a larger steering wheel.


Multiple car components use the lever to make applying force easier. For example, the gear shifting knob and many of the instrument knobs like the windshield wiper control all use lever mechanisms. A lever is something with an "arm" that turns, pivots or rotates against a single fulcrum point to provide greater force. Think of the window controls in older cars without power windows, they use a lever you rotate to lower or raise the car's windows.


Screws are simple machines with an inclined plane wrapped around a central cylinder, like a corkscrew or light bulb screw. Plenty of screws are used in cars, including the head and taillights and the very bolts that hold the car together. A modified version of the screw, called the worm gear, is used in conjunction with a gear to allow the screw to be driven by the gear but not the other way around. This type of screw sees use in your car's steering gear box.

Compound Machines

Compound or complex machines are defined as groups of simple machines working together. A car, as a whole, is the perfect example of a complex machine. Looking at the inner workings of the vehicle, like the engine components, quickly reveals that most components fit into one of the six simple machine categories. For example, the engine relies on pulleys to spin gears and screws and wheel-and-axle simple machines to generate power that's then distributed throughout the rest of the car.

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