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The ground drill, or auger, an engine-driven screwThe ground drill, or auger, an engine-driven screw A machine uses physical efforts, forces and work to get a job done. It can be as complicated as a jet engine or a combine harvester to gather crops. Yet it can be as simple as a crowbar used to lift heavy stones or a wheel on an old cart. Even the most complicated machines are combinations of a few kinds of simple machines. The main kinds of simple machines are: an inclined plane, a slope or ramp to drag or roll heavy objects upwards; a wedge, two ramps back to back as used in knife and axe blades; a lever, a rigid bar or beam that pivots on a hinge or fulcrum, like a crowbar; a screw, a wedge twisted into a corkscrew shape that forces its way through a substance; a wheel and axle, an endless curved ramp turning on its central point, the axle; a pulley, a wheel with a groove in its rim for a rope, chain or cable.

Combine harvesterCombine harvester

Machines in action

A variety of machines used to carry out a taskA variety of machines used to carry out a taskThis sequence shows how machines can be used to carry out a simple job. A crate of apples is unloaded. Pulleys reduce the amount of effort needed to raise and lower the crate from the lorry. The lid is prised open using a lever, the edge of the carton itself acting as a fulcrum. The apples are checked. One or two are samples cut open by a knife—a type of wedge with a sharp edge. The lid is fixed back on with screws (wedges twisted into corkscrew shapes). Wheels help move the crate to the van. The crate is then loaded into the van using a short ramp. It is much easier to push a heavy load up a ramp than to lift it.

A double pulley lifting mechanismA double pulley lifting mechanism


One of the earliest machines still in use today is a screw-like water-lifting device called the Archimedes screw, invented by the Greek mathematician Archimedes in about 250 BC. It consists of a screw inside a hollow pipe. As the screw turns—originally by turning a handle—the bottom end scoops up water and raises it to the top.

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