Прочитайте текст Mechanical rotational energy is required to rotate shafts in a factory for driving ...: ответ на тест 256503 - Английский язык

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There exist many sources of energy in the world both potential and kinetic. One source consists in water falling from a high level such as an upland lake. Another source is wind or moving air. Others consist in tides in the sea, heat from subterranean sources and coal deposits and oil wells yielding mineral oil.
But all these sources and stores of energy are not equally useful to mankind. Moreover some stores of energy such as coal and oil can never be replaced by us when once used up. On the other hand stores of high level water are continually being replaced by rain and wind and tides will not, as far as we know, ever cease to exist. A very important matter is the conversion of energy from one form to another. The form most required by us is mechanical rotational energy.
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Stores of high level water are continually being replaced by rain and wind and tides will not ever ________________.

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Everything happens because of energy. Without it there would be no life on Earth. Scientists classify energy into several different types, including chemical energy, light energy, and nuclear energy. Most types of energy can switch from one form to another. In a car, for example, gasoline provides chemical energy, which turns into mechanical energy, heat energy, and sound energy when the engine is started. All energy that comes from directly or indirectly from the Sun is known as radiant energy and makes up the electromagnetic spectrum.
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It may be assumed that a body consists of small particles or molecules, between which forces are acting. These molecular forces resist the change in the form of the body which external forces tend to produce. If such external forces are applied to the body, its particles are displaced and the mutual displacements continue until equilibrium is established between the external and internal forces. It is said in such a case that the body is in a state of deformation or strain. During deformation the external forces acting upon the body do work, and this work is transformed completely or partially into the potential energy of strain. An example of such an accumulation of potential energy in a strained body is the case of a watch spring. If the forces which produced the deformation of the body are now gradually diminished, the body returns wholly or partly to its original shape and during this reversed deformation the potential energy of strain, accumulated in the body, may be recovered in the form of external work.
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Molecular forces resist the change in the form of the body which external forces tend _________________.

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The property of bodies of returning, after unloading, to their initial form is called elasticity. It is said that the body is perfectly elastic if it recovers its original shape completely after unloading; it is partially elastic if the deformation, produced by the external forces, does not disappear completely after unloading. In the case of a perfectly elastic body, the work done by the external forces during deformation will be completely transformed into the potential energy of strain. In the case of a partially elastic body, part of the work done by the external forces during deformation will be dissipated in the form of heat which will be developed in the body during non-elastic deformation. Experiments show that such structural materials as steel, wood, and stone may be considered as perfectly elastic within certain limits.
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The body is perfectly elastic if it recovers its original shape completely _____________.

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Thermodynamics is that branch of physics which deals with the conversion of mechanical energy into thermal energy and the reverse process of transforming heat into work.
The production of heat by mechanical means may be illustrated by the phenomenon of friction. For example, fire may be started while rubbing together two sticks of wood. Heat is developed when compressing a gas. The transformation of heat into work may be illustrated by operation of a steam or gas engine by means of which heat may be transformed into mechanical energy.
So a heat engine is a machine for transforming heat into mechanical energy, the most important of the practical heat engines being the steam engine and the internal combustion engines.
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The production of heat by mechanical means may be illustrated _____________.

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To transform energy from any of its numerous forms into heat is a comparatively simple process. To transform heat into work is a different matter. Experience shows that any actual physical process, as the change of state of a system, is irreversible and is accompanied by frictional effect. A strictly reversible frictionless process being an ideal, it may be approached but never attained. In the case of the ideal reversible process, there is no change in the quantity of available energy; but an actual irreversible process is always accompanied by a decrease of the amount of energy available for transformation. All transformations of energy are subject to two far-reaching laws:
1. The general law of conservation of energy
2. The law of degradation of energy.
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Experience shows that any actual physical process is irreversible and is accompanied ___________________.