- This article is about devices that perform tasks.
The scientific definition of a machine is any device that transmits or modifies energy. In common usage, the meaning is restricted to devices having rigid moving parts that perform or assist in performing some work. Machines normally require some energy source ("input") and always accomplish some sort of work ("output"). Devices with no rigid moving parts are commonly considered tools, or simply devices, not machines.
Modern power tools, automated machine tools, and human-operated power machinery are tools that are also machines. Machines used to transform heat or other energy into mechanical energy are known as engines. Hydraulic devices may also be used to support industrial machines, although devices entirely lacking rigid moving parts are not commonly considered machines.
People have used mechanisms to amplify their abilities since before written records were available. Generally these devices decrease the amount of force required to do a given amount of work, alter the direction of the force, or transform one form of motion or energy into another.
Machines and the materials to make them have been major features in the betterment of humanity. While significant advances came with improvements in tools, such as plows, and the materials for making them, new levels of advance were opened with the development of machines such as wagons and chariots, grain mills and catapults, the printing press, the steam engine, and the cotton gin.
Factors driving machine development have included the effort to secure the basics of life—food, water, shelter, and clothing—from the environment, the pursuit of pure human curiosity and a thirst for understanding, and, tragically, the pursuit of military advantage over an enemy.
In the twenty-first century, the capacities of machines for improving the global human condition are unprecedented, yet these are offset by the machines’ capacities for both planned destruction in war and global side-effect destruction of the environment through the machines’ consumption of resources and generation of wastes. Such a culmination of machine influence is a factor compelling humanity toward institutions of cooperative global management.
Mechanical advantage and efficiency
The mechanical advantage of a simple machine is the ratio between the force it exerts on the load and the input force applied. This does not entirely describe the machine's performance, as force is required to overcome friction as well. The mechanical efficiency of a machine is the ratio of the actual mechanical advantage (AMA) to the ideal mechanical advantage (IMA). Functioning physical machines are always less than 100 percent efficient.
Types of machines and other devices
|Simple machines||Inclined plane, Wheel and axle, Lever, Pulley, Wedge, Screw|
|Mechanical components||Gear, Rope, Spring, Wheel, Axle, Bearings, Belts, Seals, Roller chains, Link chains, Rack and pinion, Fastener, Key|
|Clock||Atomic clock, Chronometer, Pendulum clock, Quartz clock|
|Compressors and Pumps||Archimedes screw, Eductor-jet pump, Hydraulic ram, Pump, Tuyau, Vacuum pump|
|Heat engines||External combustion engines||Steam engine, Stirling engine|
|Internal combustion engines||Reciprocating engine, Wankel engine, Jet engine, Rocket, gas turbine|
|Turbine||Gas turbine, Jet engine, Steam turbine, Water turbine, Wind generator, Windmill (Air turbine)|
|Airfoil||Sail, Wing, Rudder, Flap, Propeller|
|Electronic machines||Computing machines||Calculator, Computer, Analog computer|
|Electronics||Transistor, Diode, Capacitor, Resistor, Inductor|
|Biological machines||Virus, Bacterium, Cell (biology), Plant and animal, DNA computers, Human being|
|Miscellaneous||Robot, Vending machine, Wind tunnel|
- Boothroyd, Geoffrey and Winston A. Knight. 2005. Fundamentals of Machining and Machine Tools, Third Edition (Mechanical Engineering (Marcell Dekker)). Boca Raton, FL: CRC. ISBN 1574446592.
- Myszka, David H. 1998. Machines and Mechanisms: Applied Kinematic Analysis. Upper Saddle River, NJ: Prentice Hall. ISBN 0135979153.
- Oberg, Erik, Franklin D. Jones, Holbrook L. Horton, and Henry H. Ryffel. 2000. Machinery's Handbook. New York, NY: Industrial Press Inc. ISBN 0-8311-2635-3.
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