Thrust

“ Some of these great thrusts have received distinguishing names, e.g. the Moine thrust (fig. 19) and the Ben More thrust; similarly in the coal basin of Mons and Valenciennes we find the faille de Boussu and the Grande faille du midi. Overturned folds are frequently seen passing into thrusts. ”

“ It had been known for centuries that light had both mass and pressure, and here it was concentrated matter—the ultimate in propulsive thrust—changed completely to energy. On the sullen Earth, neither man nor android dared watch that thin thread of fury, while slowly the ship began to accelerate toward a five-figure number of miles per second. ”

“ The more they studied it, the more complex the problem became. “The thrust depends upon the speed and the angle at which the blade strikes the air; the angle at which the blade strikes the air depends upon the speed at which the propeller is turning, the speed the machine is traveling forward, and the speed at which the air is slipping backward; the slip of the air backward depends upon the thrust exerted by the propeller, and the amount of air acted upon.” ”

“ III.—The constancy of demonstrated in the present proposition has for an immediate consequence the constancy of the gliding angle (if be ignored) , that is to say, the thrust required to maintain an aerodrome in flight will be constant for a given value of and if this thrust be supplied by a component of gravity (Fig. 110) , and if be the angle of descent, we have:—
that is to say, is constant. If we take account of the body resistance , we shall find that the value of will increase the higher the velocity. ”

“ It is conceived that where strong thrusts are brought to bear upon such a mass of granules, those whose gliding planes are parallel to the direction of thrust are strained with sufficient intensity to cause the plates to slide over each other, while those which are not parallel to the direction of thrust are either rotated into parallelism—when they also yield—or are pressed aside out of the plane of shear. As previously noted, shearing318 is observed to occur chiefly where the ice below the plane of shearing is protected more or less from the force of the thrust. ”

“ For if the body is removed, and replaced by the fluid as at first, this fluid is in equilibrium under its own weight and the thrust of the surrounding fluid, which must be equal and opposite, and the surrounding fluid acts in the same manner when the body replaces the displaced fluid again; so that the resultant thrust of the fluid acts vertically upward through the centre of gravity of the fluid displaced, and is equal to the weight. ”

“ It is very evident, though, that for most cases in practice, the formulas give a very appreciable excess over the true thrust, and that the true plane of rupture never coincides with the natural slope. ”

“ A bar or rod or wire of any substance with or without a weight hung on it, or experiencing any degree of end thrust, to begin with, becomes cooled if suddenly elongated by end pull or by diminution of end thrust, and warmed if suddenly shortened by end thrust or by diminution of end pull ”

“ In a large pitch angle so much energy is wasted, not in dynamic thrust, but in transverse upsetting torque. On no propeller out of dozens and dozens that I [77] have tested have I ever found a tip-pitch of more than 35° give a good dynamic thrust; and for length of flight velocity due to dynamic thrust must be given due weight, as well as the duration of running down of the rubber motor. ”

“ But it is sufficiently known, that air will penetrate water by the application of a force equal to the gravity of the water. If therefore the force, by which the vessel is thrust down, be greater or equal to the endeavour by which the water naturally tendeth downwards, the air will go out that way where the resistance is made, namely, towards the edges of the vessel. For, by how much the deeper is the water which is to be penetrated, so much greater must be the depressing force. ”

“ On second thought, one reverts to the people who are always trying to fight their way up that adverse current, with the thrust of two miles perpendicular descent and the body of a thousand storms in its rush. ”

“ Make a thrust. Thrust, n. 1. Push, shove, pass, stab, allonge, lunge, tilt. 2. Assault, attack, charge. Thrust one's nose in, [Colloquial.] Interfere, meddle, intermeddle, PUT IN ONE'S OAR. Thrust one's self, Obtrude, intrude. Thud, n. 1. Shock, impetus. 2. Stroke, blow, thump, knock. Thump, n. Blow, knock, stroke. Thump, v. a. Beat, knock, strike, belabor. Thunder-clap, n. Thunder-stroke. Thunder-shower, n. Thunder-storm. Thunder-storm, n. Tempest (accompanied with thunder and lightning) , thunder-shower. Thunder-stroke, n. Thunder-clap. ”

“ The process of ‘backing up’ is excessively fatiguing, the thrust necessary to hold oneself firmly in situ being as a rule much greater than the equivalent of one’s weight, and the whole of this thrust being at every slight lift transmitted through the arms. ”

“ It is likewise subjected to a thrust from the earth, corresponding to and , for the saturated material, but with a weight per cubic foot equal to that of the earth in air less the buoyant effect of the water. ”

“ For, if the earth below was removed, the thrust on would have to be sufficient to prevent the whole mass, , from descending, which is far greater than , which balances only the thrust of the wedge of rupture, the inclined base of which passes through . ”

“ When a thrust tangentially affects a stratified mass, it is transmitted in the direction of the strata, and by each stratum according to its inflexibility. At any bend the force is resolved into components, one radial, the other tangential to the dip beyond the bend ”

“ Barnaby in 1894, and by them it was experimentally determined that cavitation, or the hollowing out of the water into vacuous spaces and vortices by the blades of the propeller, commences to take place when the mean thrust pressure on the projected area of the blades exceeds eleven pounds and a quarter per square inch. ”

“ In fact, if is the normal component of the thrust on the plane, , is all the friction that can be exerted on it. The resultant of and thus makes an angle, , with , and this angle cannot be exceeded. The true thrust on the wall, , is thus the greatest of the trial thrusts, . The prism of rupture, , is in equilibrium under the four forces represented by the sides of the closed polygon ”

“ The assumption is that the tendency of the material to slide toward the toe causes it to wedge itself between the face of the sheeting on the one hand and some plane between the sheeting and the plane of repose on the other, and that the resistance to this tendency will cause an arching thrust to be developed along or parallel to the lines, A N, B M, etc., Fig. ”

“ When one portion of the mass begins to lag it may be thrust forward bodily by great pressure from behind, compelled to mount reverse slopes, to scour the bed, detach rock fragments and transport whatever material finds lodgment within or upon the mass. ”

“ When the left arm has completed these movements, it, in its turn, is lifted from the water, stretched forward, and pulled back,—the right arm describing first the smaller, then the larger circle. The feet make their movements during the describing of the larger circle. The thrust requires much practice; but, when well acquired, it not only relieves the swimmer, but enables him to make great advance in the water, and is applicable to cases where rapidity is required for a short distance. ”

“ It consists in the fore and hind foot of one side being raised simultaneously, and thrust forward. In this movement, the greater or less speed depends on the degree in which the hind foot is advanced in comparison with the fore one. ”

“ Most of the faults committed in making thrusts when the measure is to be closed, proceed from the disorder of the body, occasioned by that of the feet, so that for want of moving well, you are not only in danger of being taken on your time, but likewise you cannot execute your thrusts neatly, justly, nor swiftly; the body being disordered and weak. ”

“ These powerful lateral thrusts of the external and solid parts of the globe appear to result from a diminution which the radius of the interior pasty or fluid nucleus has undergone during millions of ages. ”

“ To seek to press a falling body by means of another placed upon it, is as senseless as trying to prod a man with a lance when the man is speeding away from one with the same velocity as the lance. Even this little excursion into physics can explain much to us. You know the peculiar sensation which one has in falling, as when one jumps from a high springboard into the water, and which is also experienced in some measure at the beginning of the descent of elevators and swings. ”

“ The water at the head of a weir is passing every instant from slower into quicker motion; but (until broken in the air) the fast flowing water is just as dense as the slowly flowing water. But a fan alternately compresses and rarefies the air between it and the cheek, and the violence of a destructive gust in a gale of wind means a momentary increase in velocity and density of which I cannot myself in the least explain,—and find in no book on dynamics explained,—the mechanical causation. ”

“ But the liquid after it leaves the vessel is subject to no forces except gravity, the pressure of the air, and its own surface-tension. Of these gravity has no effect on the form of the stream except in drawing asunder its parts in a vertical direction, because the lower parts are moving faster than the upper parts. The resistance of the air produces little disturbance until the velocity becomes very great. ”

“ The problem of flight thus resolves itself into one of weight, power, velocity, and small surfaces; versus buoyancy, debility, diminished speed, and extensive surfaces,—weight in either case being a sine quâ non. In order to utilize the air as a means of transit, the body in motion, whether it moves in virtue of the life it possesses, or because of a force superadded, must be heavier than the air. It must tread and rise upon the air as a swimmer upon the water, or as a kite upon the wind. ”

“ This power may be applied in various ways. A large body, of the heaviest materials that will float, may first be raised by it, and being attached to the end of a balance reaching from the land, or from a stationary support, fastened to the bottom, when the tide falls, the whole weight will be brought to bear upon the end of the balance. Also, when the tide rises, it may be made to exert a nearly equal force in the opposite direction. ”

“ That the descent is a mechanical effect of the whirlwind, which creating a vacuum, or high degree of rarefaction, extending between the clouds and the earth, the clouds descend in it by their gravity, or by the pressure of the surrounding clouds or air. That the convolutions of the descending mass, and the sensible whirlwind felt at the earth, as well as the appearance of the commencement, increase and decrease of the mass, all demonstrate the whirl of the air to be the mechanical cause. ”

“ II. The spaces run thro’ by falling bodies are proportional to one another as the squares of their last or acquired velocities.
These two principles are demonstrated by the writers on mechanics.
III. Water forced out of a larger chanel thro’ one or more smaller passages, will have the streams thro’ those passages contracted in the ratio of 25 to 21.
This is shewn in the 36th prop. of the 2d book of Newton’s Principia.
IV. In any stream of water, the velocity is such, as would be acquired by the fall of a body from a height above the surface of that stream. ”

“ If the finest sand were thrown against our bodies with the hundredth part of this velocity, each grain would pierce us as certainly as the sharpest and swiftest arrows from a bow. It is a principle in mechanics that the force with which all bodies strike, is in proportion to the size of these bodies, or the quantity of matter they contain, multiplied by the velocity with which they move. ”

“ The force of the wind, as transmitted by degrees to the sea, is manifested as a series of progressing undulations without any material displacement of the body of water, each undulation transmitting its accumulated force to the next in the direction the wind is blowing, till at last, on encountering an obstacle to its onward course, each wave, no longer finding any water to which to communicate its energy, deals a blow against the obstacle proportionate to its size and rate of transmission ”

“ To these and other considerations the doctor adds, that the strokes which ships receive during an earthquake, must be occasioned by something which can communicate motion with much greater velocity than any heaving of the earth under the sea, caused by the elasticity of generated vapors, which would merely produce a gradual swell, and not such an impulsion of the water as resembles a violent blow on the bottom of a ship, or its striking on a rock. ”

“ Running at a speed of twelve or fifteen miles an hour, we hit the water with a tremendous shock, bounded thirty or forty feet into the air, descended again and literally skipped in great leaps along the surface of the water, precisely like a well-thrown "skipping stone." ”

“ At length a loud crack is heard, like the report of a cannon—then another, and another—and finally the loosened mass begins to move towards the ocean. The motion at first is almost imperceptible, but it gradually increases in velocity, as the impetus of the descending ice above propels it along ”

“ The explanation of this phenomenon appears to me to be as follows: a wing, or any surface whatever, which moves against the air, meets, at the beginning of its motion, a considerable resistance, on account of the inertia of the air, which resists every displacement; but, little by little, the air yields, and the velocity of its motion gradually increases, until it may equal that of the moving surface which displaces it; this phase of motion having been reached, the resistance diminishes. ”