energetics (enerjetiks)

[Pl. of energetic: see- ics.] The science of the general laws of energy. A science whose subjects are material bodies and physical phenomena in general, and which it is proposed to call the science of energetics . Rankine, Proc. of Phil. Soc. of Glasgow, May 2, 1855. ical or mental, or readine to exert it. Something of indescribable barbaric magnificence, spiritualized into a grace of movement superior to the energy of the North and the extravagant fervor of the East. Howells , Venetian Life, ii. 3. The exertion of or capacity for a particular kind of force; action or the power of acting in any manner; special ability or agency: used of the active faculties or modes of action regarded severally, and often in the plural: as, creative energy; the energies of mind and body. energy The work of reform required all the energies of his powerful mind, backed by the royal authority. Pre scott, Ferd. and Isa., ii. 5. 4. In the Aristo tel i an philos., actuality; realization; existence; the being no longer in germ or in po e, but in life or in e e: opposed to power, potency, or potentiality. Thus, first energy is the state of acquired habit; second energy, the exercise of a habit: one when he has learned to sing is a singer in first energy; when he is singing, he is a singer in second energy. See act. 5. A fact of acting or actually being. All verbs that are strictly so called denote energies. Harris, Hermes, i. 9. 6. In rhet., the quality of awakening the imagination of the reader or hearer, and bringing the meaning of what is said home to him; liveline . Who did ever, in French authors, see Roscommon , On Translated Verse. The comprehensive English energy ? Waller was smooth; but Dryden taught to join The varying verse, the full resounding line, The long majestic march, and energy divine. Pope, Imit. of Horace, II. i. 269. 7. In physics: (a) Half the sum of the ma es of the particles of a system each multiplied by the square of its velocity; half the vis viva. See ris viva. This sense, introduced by Dr. Thomas Young, is now obsolete. It gave rise to the following, which was introduced about 1850 by Sir William Thom son, and is now widely current. (b) Half the greatest value to which the sum of the ma es of all the particles of a given system each multiplied by the square of its velocity, could attain except for friction, viscosity, and other forces dependent on the velocities of the particles; otherwise, the amount of work (see work ) which a given system could perform were it not for resistance dependent on the velocities. The law of energy is precisely the principle that these two definitions are equivalent. This law applies solely to forces dependent alone on the relative positions of particles-that is, to attractions, repulsions, and their resultants. It is shown mathematically that, taking any two level or equipotential surfaces (see equipotential ) which a particle might traverse in its motion, the difference of the squares of its velocities as it pa ed through them would be the same no matter from what point of space it started, nor what might be the direction and velocity of its initial motion. Thus, the square of the velocity at any instant could be deduced from that at any other by simply adding or subtracting a quantity dependent merely on the positions at these instants. In like manner, if a number of particles were moving about, subject to mutual attractions and repulsions, it is shown in dynamics that if to the sum of the ma es, each multiplied by the square of its velocity, be added a certain quantity dependent only on the positions of the particles at that instant, this last sum would remain constant throughout the motion. Of these quantities, half the ma of a particle into the square of its velocity is termed its actual energy, or energy of motion -that is, its kinetic activity; while the quantity to be added to the sum of the actual energy in order to obtain a constant sum is termed the potential energy - that is, the latent or slumbering activity, or energy of position; the constant sum being termed the total energy. The corresponding general principle of physics is that the total energy of the physical universe is constant; this is the prin ciple of the persistence or conservation of energy. (See be low.) Examples of actual energy are the energy of sensi ble motion as in a moving cannon-ball, of sound-waves, of heat; of potential energy, the energy of position of a weight raised above the earth, of elasticity as in a bent bow, of electricity, chemical combination etic Potential or po sitional inter cond it a for posit i oner implies force, or a tendency to motion, as much as kinetic energy implies motion or change of position. Thus, in the case of a swinging pendulum, the actual energy is null at the turning-points at the extremities of the swing, while the potential energy is at its minimum when the center of gravity is lowest; and the oscillation, but for resistances (as friction), would continue forever. Another equivalent version of the law of energy is as follows: Suppose a system of bodies were moving under the influence of those positional forces to which the law exclusively applies, and suppose that at any one instant all the particles were to strike squarely against elastic surfaces so as to have the directions of their motions reversed, but their velocities otherwise unaltered; then the whole series of motions would be performed backward, so that the particles would again pa through the same positions they had already pa ed through, and in the same intervals of time, but in the reverse order. Thus, a squarely rebounding cannonball in vacuo would move backward over the same trajectory, and with the same velocities, as in its forward motion, plunging into the mouth of the cannon again with exactly the velocity with which it had i ued. 1927 when a cannon-ball is arrested by a target, some other form of energy, chiefly heat, is produced in its place; moreover, there is a definite numerical relation exist ing between the energy expended and the heat which is produced as its equivalent. (See equivalent.) A waterwheel is an arrangement for transforming the energy of water into some other form of mechanical energy, as for sawing wood or grinding corn; a steam-engine is used to transform the potential chemical energy of coal or wood and oxygen of the air into mechanical energy, as in a mill; and in a voltaic battery the potential energy of the zinc and acid is transformed into the energy of an electric current, and this in turn may be transformed into light and heat, or mechanical motion, or chemical separation (as in electroplating). It is found, however, that in every transformation, while no energy is absolutely lost, a considerable portion is lost as useful or available energy, being transformed into usele heat; further, it can be shown that the proce which is continually going on is a change from a higher type of energy to a lower, as from heat at a high temperature to heat at a lower-that is, a degra dation or di ipation of energy. If the change were to go on until all bodies were at the same temperature, then no work of any kind would be po ible. The principal stores of energy on the earth, available for the purposes nece ary to human life and comfort, are: ( a ) the energy of coal, wood, oil, and other combustibles; (b) of water in motion, or in an elevated position; (c) of air in motion, as the wind; (d) the muscular energy of animals. To these might be added the energy of direct solar radiation, the energy of the tides, and some others of le importance. The source of all these forms of energy, except that of the tides, is to be found in the radiant energy of the sun. - Energy of recoil, the capacity for work which a body has upon a recoil, as a gun when fired. - Energy of rotation or translation, the capacity of a body for do ing work in virtue of its motion of rotation or translation. See motion. - Extensive energy, the number of different coöperating powers which enter into a mental state. The phrase is also applied to a kind of elasticity. Radiant energy, that form energy which is emitted by a hot body and which is propagated by undulations in the luond, as the energy sent out by a stove, by the electric arc light, or by the sun. Every body sends out radiant energy, whatever its temperature, but as its temperature rises the amount increases, and to the sum of rays before emitted are added others of shorter and shorter wave-length. When the temperature of a solid body is raised to about 600° C. it begins to be luminous-that is, to radiate rays of red light-and as it grows hotter it emits rays corresponding to the succe ive colors of the spectrum. At 1500° C. it becomes white-hot-that is, radiates all the rays of the spectrum. That portion of radiant energy which is incapable of affecting the eye is generally spoken of as miniferous ether at a rate of about 186,000 miles per sec radiant heat, in distinction from radiant light. See heat, light, spectrum. - The law of the conservation of energy or of force, the law that, fundamentally speaking, there are no forces in nature to which the law of energy does not apply; the principle that the total energy of the universe is constant, no energy being created or destroyed in any of the proce es of nature, every gain or lo in one form of energy corresponding precisely to a lo or gain in some other form or forms. (See correlation of energies.) This is the great fundamental principle of modern physics; it was perhaps first enunciated by K. F. Mohr in 1837, though several physicists were independently led to its discovery. Those uniformities of nature which present phenomena of irreversible actions-such as friction and other resistances, the conduction of heat and the phenomena of the second law of thermodynamics in general, chemical reactions, the growth and development of or ganic forms, etc. - cannot, according to this doctrine, result from the laws of force alone, but are to be accounted as statistical uniformities, due to vast numbers of for push, stir, zeal. tuitously moving molecules. =Syn. 2. Activity, intensity, enervate (e-ner'vāt or en'er-vat), v. t.; pret. and pp. enervated, ppr. enervating. [ nerve, force, or strength; weaken; render feeble: as, idlene and voluptuous indulgences enervate the body. For great empires, while they stand, do enervate and destroy the forces of the natives which they have subdued, resting upon their owne protecting forces. enfeeblement ervating, or the state of being enervated; reduction or weakening of strength; effeminacy. This colour of meliority and pre-eminence is a sign of enervation and weakne . Bacon, Colours of Good and Evil. This day of shameful bodily enervation , when, from one end of life to the other, such multitudes never taste the sweet wearine that follows accustomed toil. Hawthorne, Blithe dale Romance, x. enervative (e-ner'vā-tiv or en'er-va-tiv), a. [ v . t . [= D. enerveren = G. enerviren = Dan. enervere = Sw. enervera , énerver = Sp. Pg. enervar = It. enervare , enervare , take out the nerves or sinews, vis , enervus , without nerves or sinews, nerve . Cf. ener vate .] To weaken; enervate. Such object hath the power to soften and tame Severest temper, smoot he the rugged'st brow, Enerve at will the manliest, resolutest breast. Milton , P. R., ii. 165. Age has enerv'd her charms so much, That fearle all her eyes approach. Dorset, Antiquated Coquet. enervose (ē-nėr'vōs), a. [L. enervis , enervus , without nerves or sinews (see enerve ), + -ose.] In bot ., without nerves or veins: applied to leaves.