Physical force

“ The term physical is further employed to denote certain "affections of matter"—that is, mechanical effects which are the result of the action of force upon matter. It is true we often speak of "physical forces," as though force were an essential attribute of matter. ”

“ Having now defined the use of the term force, and shown that forces are correlated which are convertible 44and mutually dependent, we go on to study the evidences of such correlation among the motions of inorganic nature usually called physical forces; and to ask what proof science can furnish us that mechanical motion, heat, light, and electricity are thus mutually convertible. ”

“ Force, with physical motion, and gravity, with resistance, are the four accidental powers by which all mortal things live and die. Force has its origin in spiritual motion, and this motion, flowing through the limbs of sentient animals, enlarges their muscles, and thus enlarged the muscles are shrunk in length and contract the tendons with which they are connected, and this is the cause of the strength in human limbs. The quality and quantity of the strength of a man can generate a further force, which will increase in proportion to the duration of the motions produced by them. ”

“ All that we mean by physical force is a force which acts upon matter, and produces in the motions and collocations of matter its appropriate effects. [509] Spirit-force is the only force in the universe; all that our physical science deals with is "forms of energy which have their origin in force." ”

“ Now, by this sense, we obtain a perception of force as pressure, distinct and unique, and not involving the variable element of distance, which enters into the perception of force as derived from the sense of sight alone. ”

“ With each elevation there is a peculiar force added to the already existing, and a peculiar group of phenomena is the result. As matter only rises step by step from plane to plane, and never two steps at a time, so also force, in its transformation into higher forms of force, rises only step by step. Physical force does not become vital except through chemical force, and chemical force does not become will except through vital force. ”

“ His theory is that this force, whatever its actual nature may be, is universally present, and operates as a current of physical vitality perpetually, flowing with more or less energy through every physical organism, and which can, at any rate to some extent, be controlled by the power of the human will. ”

“ All our knowledge of mechanical forces is derived from the conscious effort we ourselves make in producing motion. As this motion employs the machinery of contact, the force of gravitation is wholly outside of all our experience. ”

“ In the phraseology of our mechanics we define matter and force as if they had an independent existence. But we have no conception of inert matter or of disembodied force. All we know of matter is its pressure and its motion. ”

“ The persistency of force means also the persistency of motion. All forms of physical energy—as light, heat, sound, electricity, magnetism, chemical action, gravity and sensible motion—he says, are different manifestations of force. ”

“ Vital force was generally regarded as something which in a living body was united with physical matter and forces in the same way that the force of a magnet unites itself with iron. Then came the time when vital force was banished from the domain of science. Mere physical and chemical causes were accounted all sufficient. ”

“ Cause then becomes the synonym of force. But physical science defines force only by its effects:—movement, or work done. So, too, the biologist rejects the notion of “vital force”; non-metaphysical psychology will have none of the “faculties,” intervention of “the soul,” and the like. Is the notion thus discarded, totally suppressed? Nay,—for even in mechanics and physics it cannot be entirely eliminated. It is there as a postulate, a residuum, an unknown factor covering lacunæ. ”

“ And beyond his form no physical progress seems possible, for he fulfills what we conceive to be Nature's design, viz., to husband force by the fullest avoidance of gravity and friction, to decrease weight to the lowest available point consistent with the size and strength necessary to best adapt him to surrounding conditions, and to produce the utmost susceptibility to impression of natural force—to attain a form, in fact, having the greatest excess of available energy, and best adapted to gain experiences of the conditions of nature. ”

“ In these speculations, the force of gravity is resolved into the pressure or impulse of solids or fluids. On the other hand, hypotheses have been propounded, in which the solidity, and other physical qualities of bodies, have been explained by representing the bodies as a collection of points, from which points, repulsive, as well as attractive, forces emanate. ”

“ Many of the most eminent thinkers of the present time are disposed to regard all the active principles of nature as “modes of motion,”—to look upon light, heat, electricity, and even vital force, as phenomena resulting from “change of place” among the particles of matter; this change, disturbance, or motion, being dependent upon some undefined mover. ”

“ The fundamental principle of action in such media must be in accordance with elastic impact, for upon that the dynamic theory of heat and conservation of force rests as a foundation. The statical and dynamical characteristics of gravitation and transfusion of force conform to it, so that all the forces that hold the molecules of bodies together must also be in subjection to it. ”

“ Thus the march onward proceeds, and when some general law of Nature—like, for instance, gravitation, the correlation of the physical forces, or, even, with a more limited bearing, reflex spinal action—is discovered, a gain is made which, through reflected influence, has the effect of at once immensely enlarging and perfecting the understanding. ”

“ It must be acknowledged by all who have witnessed, under test conditions, any of the physical phenomena, that there is a dynamic force residing somewhere that is capable of moving ponderable objects without physical contact, and that this force, whatever it is, or from whatever source it emanates, possesses intelligence, oftentimes to a remarkable degree. ”

“ Using the phraseology of physical science may help a good deal to understand what we mean. Of the total force of every action of a man–including thought and word also in the word action–one part goes off as kinetic energy and that is represented by its visible effects that appear immediately the action is ended. ”

“ The first great agent which the analysis of natural phenomena offers to our consideration, more frequently and prominently than any other, is force. Its effects are either, 1st, to counteract the exertion of opposing force, and thereby to maintain equilibrium ”

“ If it were true that there is a necessary relation between vigor of body and vigor of mind; that mental power is proportional to physical power; that thought is but a special form of energy and capable of transformation, like heat, light and electricity; that it, like the various physical forces, has its chemical and mechanical equivalents; that psychic work corresponds to a certain amount of chemical or thermic action; that intellectual capacity in man is proportional to muscular strength ”

“ Every form, whether inorganic or organic, which we can discover within the limits of human search, is composed of atoms, which are capable of assuming, under the influence of certain physical forces, conditions essential to the physical state of that body of which they constitute a part. [1] The known forces, active in pro [Pg 5] ducing these conditions, are modes of motion; gravitation and aggregation, heat, light; and associated with these, actinism or chemical radiation; electricity, under all its conditions, whether static or dynamic ”

“ Are physical forces alone at work there, or has evolution begotten something more complex, something not unakin to what we know on Earth as life? ”

“ It is from our dynamic Activity also that we derive our conception of Force. Force, though it is studied scientifically in the measurement of the great natural forces which operate constantly, is originally known to us in the stress or pressure to which muscular exertion in contact with a material body gives rise. Such a force if it could be correctly measured, would record the rate at which Energy was undergoing transmutation, and it is from such experience of pressure that our idea of Force is originally derived. ”

“ Bearing in mind the conservation of forces, that energy or power is as indestructible as matter, that it may be changed into other forms but never lost, it is plain that mechanical force may be applied to the living system and transformed into vital energy; that chemical action, animal heat, and magnetism may represent in the system the mechanical force transmitted to the body. ”

“ These subjects are the elements of mechanics; they form the framework which in this and subsequent lectures we shall try to present in a more attractive garb. We shall commence by studying the most remarkable force in nature, a force constantly in action, and one to which all bodies are subject, a force which distance cannot annihilate, and one the properties of which have led to the most sublime discoveries of human intellect. This is the force of gravity. ”

“ Let us now consider with more attention the general physiological law that quantity of power is in proportion to the size of the body. This brings us to the still more fundamental principle of the inseparability of matter and force. ”

“ This element is in animals and men produced by their inherent dynamic force, counteracted by the body itself, which represents the static force, or the ‘vis inertiæ,’ chaining them to the centre of gravitation in the earth. ”

“ Büchner. Physics, as I stated to you on another occasion, “makes us acquainted with eight different forces—gravitation, mechanical force, heat, light, electricity, magnetism, affinity, cohesion, which, inseparably united to matter, form and give shape to the world. These [pg 643] forces are, with few exceptions, mutually convertible, so that nothing is lost in the process of conversion” (p. 18) . ”

“ Yet in mechanics, whatever the mechanicians might think, both energies acted as interchangeable forces on man, and by action on man all known force may be measured. Indeed, few men of science measured force in any other way. ”

“ He measured forces by the weight and speed of the bodies and arrived at an approximation of the ideas of mechanical "work" and energy of position. He thought of energy as a spiritual force transferred from one body to another by touch. ”

“ Have not the small particles of bodies certain powers, virtues, or forces, by which they act at a distance? .... What I call 'attraction' may be performed by impulse, or by some other means unknown to me. I use that word here to signify only in general any force by which bodies tend toward one another, whatsoever be the cause. ”

“ Stress.—Every body that we know anything about is always under the action of forces. Every body upon which we can experiment is subject to the force of gravity, and must, for the purpose of experiment, be supported by other forces. Such forces are usually applied by way of pressure upon a portion of the surface of the body; and such pressure is exerted by another body in contact with the first. The supported body exerts an equal and opposite pressure upon the supporting body across the portion of surface which is common to the two. ”

“ Under the head of “Mixed Mathematics,” applicable to both laws or abstract principles and facts, the discussion of things as actual and possible, we have first, mechanics, the science that treats of the various forces and their different effects. By force is meant any power that tends to prevent, produce, or modify motion. Three are recognized— (1) gravitation, or the attraction of bodies toward each other; (2) the cause, whatever it may be, of light, heat, and electricity; (3) life, an equally mysterious power producing the actions of animals and the growth of plants. ”

“ All bodies have this attraction for each other, but in small bodies we do not observe it. Its force is due to the [Pg 54] weight or mass of the bodies, and diminishes as their distance from each other increases. ”

“ Every objective manifestation, whether it be the motion of a living limb, or the movement of some inorganic body, requires two conditions: will and force—plus matter, or that which makes the object so moved visible to our eye; and these three are all convertible forces, or the force-correlation of the scientists. ”

“ By Cause we mean some quality, power, or efficacy, by which a state of things produces a succeeding state. Thus the motion of bodies from rest is produced by a cause which we call Force: and in the particular case in which bodies fall to the earth, this force is termed Gravity. In these cases, the Conceptions of Force and Gravity receive their meaning from the Idea of Cause which they involve: for Force is conceived as the Cause of Motion. ”

“ My understanding of the doctrine is, that there are five chief powers or forces in Nature: one mechanical, or molar, the momentum of moving matter; the others molecular, or embodied in the molecules, also supposed in motion—these are, heat, light, chemical force, electricity. To these powers, which are unquestionable and distinct, it is usual to add vital force, of which, however, it is difficult to speak as a whole; but one member of our vital energies, the nerve-force, allied to electricity, fully deserves to rank in the correlation. ”

“ In both of the illustrations now given, we have used the force of gravity as that force against which we are to do work, and in virtue of which a stone high up, or a head of water, is in a position of advantage, and has the power of doing work as it falls to a lower level. But there are other forces besides gravity, and, with respect to these, bodies may be in a position of advantage and be able to do work just as truly as the stone, or the head of water, in the case before mentioned. ”