machine (redirected from machines)

machine, arrangement of moving and stationary mechanical parts used to perform some useful work or to provide transportation. From a historical perspective, many of the first machines were the result of human efforts to improve war-making capabilities; the term engineer at one time had an exclusively military connotation. In the United States the original colonies were not permitted to make or import machine tools; it was only after the Revolution that the first manufacturing machines were built (c.1790) by Samuel Slater for a textile mill in Pawtucket, R.I.

Types of Machines

By means of a machine an applied force is increased, its direction is changed, or one form of motion or energy is changed into another form. Thus defined, such simple devices as the lever, the pulley, the inclined plane, the screw, and the wheel and axle are machines. They are called simple machines; more complicated machines are merely combinations of them. Of the five, the lever, the pulley, and the inclined plane are primary; the wheel and axle and the screw are secondary. The wheel and axle combination is a rotary lever, while the screw may be considered an inclined plane wound around a core. The wedge is a double inclined plane.

Complex machines are designated, as a rule, by the operations they perform; the complicated devices used for sawing, planing, and turning, for example, are known as sawing machines, planing machines, and turning machines respectively and as machine tools collectively. Machines used to transform other forms of energy (as heat) into mechanical energy are known as engines, i.e. the steam engine or the internal-combustion engine. The electric motor transforms electrical energy into mechanical energy. Its operation is the reverse of that of the electric generator, which transforms the energy of falling water or steam into electrical energy.

Mechanical Advantage and Efficiency of Machines

By means of a machine, a small force, or effort, can be applied to move a much greater resistance, or load. In doing so, however, the applied force must move through a much greater distance than it would if it could move the load directly. The mechanical advantage (MA) of a machine is the factor by which it multiplies any applied force. The MA may be calculated from the ratio of the forces involved or from the ratio of the distances through which they move. Ideally, the two ratios are equal, and it is simpler to calculate the ratio of the distance the effort moves to the distance the resistance moves; this is called the ideal mechanical advantage (IMA). In any real machine some of the effort is used to overcome friction. Thus, the ratio of the resistance force to the effort, called the actual mechanical advantage (AMA), is less than the IMA.

The efficiency of any machine measures the degree to which friction and other factors reduce the actual work output of the machine from its theoretical maximum. A frictionless machine would have an efficiency of 100%. A machine with an efficiency of 20% has an output only one fifth of its theoretical output. The efficiency of a machine is equal to the ratio of its output (resistance multiplied by the distance it is moved) to its input (effort multiplied by the distance through which it is exerted); it is also equal to the ratio of the AMA to the IMA. This does not mean that low-efficiency machines are of limited use. An automobile jack, for example, must overcome a great deal of friction and therefore has low efficiency, but it is extremely valuable because small effort can be applied to lift a great weight.

Although most machines are used to multiply an effort so that it may move a greater resistance, they may have other purposes. For example, a single, fixed pulley merely changes the direction of the applied force; the pulley may make it easier to lift the load, since a person can pull down on a rope, thus adding his or her own weight to the effort, rather than simply lifting the load. In a catapult an effort greater than the load moves through a short distance, causing the load to be moved through a large distance before being released. As the load is being moved, it picks up speed so that it is traveling at a considerable velocity when it leaves the catapult.

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machine

Device that amplifies or replaces human or animal effort to accomplish a physical task. A machine may be further defined as a device consisting of two or more parts that transmit or modify force and motion in order to do work. The five simple machines are the lever, the wedge, the wheel and axle, the pulley, and the screw; all complex machines are combinations of these basic devices. The operation of a machine may involve the transformation of chemical, thermal, electrical, or nuclear energy into mechanical energy, or vice versa. All machines have an input, an output, and a transforming or modifying and transmitting device. Machines that receive their input energy from a natural source (such as air currents, moving water, coal, petroleum, or uranium) and transform it into mechanical energy are known as prime movers; examples include windmills, waterwheels, turbines, steam engines, and internal-combustion engines.

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machine

Any electronic or electromechanical unit of equipment. A machine is always hardware; however, "engine" refers to hardware or software.

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machine

1. an assembly of interconnected components arranged to transmit or modify force in order to perform useful work

2. a device for altering the magnitude or direction of a force, esp a lever, screw, wedge, or pulley

3. a mechanically operated device or means of transport, such as a car, aircraft, etc.

4. any mechanical or electrical device that automatically performs tasks or assists in performing tasks

5. (esp in the classical theatre) a device such as a pulley to provide spectacular entrances and exits for supernatural characters

6. an event, etc., introduced into a literary work for special effect

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machine [mə′shēn]

(computer science)

A mechanical, electric, or electronic device, such as a computer, tabulator, sorter, or collator.

A simplified, abstract model of an internally programmed computer, such as a Turing machine.

(mechanical engineering)

A combination of rigid or resistant bodies having definite motions and capable of performing useful work.

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Machine

A combination of rigid or resistant bodies having definite motions and capable of performing useful work. The term mechanism is closely related but applies only to the physical arrangement that provides for the definite motions of the parts of a machine. For example, a wristwatch is a mechanism, but it does no useful work and thus is not a machine. Machines vary widely in appearance, function, and complexity from the simple hand-operated paper punch to the ocean liner, which is itself composed of many simple and complex machines. See Machinery, Simple machine

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machine - Common term for "computer", usually when considered at the hardware level. The Turing Machine, an early example of this usage, was however neither hardware nor software, but only an idea.