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acting applied attached attraction axis balance beam body brass called cause centre of gravity centre of oscillation centrifugal force circumference compensation continued cord curve cylinder descend diameter diminished DIONYSIUS LARDNER direction distance earth effect equal expansion explained fall feet final velocity fixed force of gravity friction fulcrum greater gridiron pendulum horizontal inches inclined plane increased inertia iron length lever load machine manner mass mechanical mercury moment of inertia move multiplied necessary observed ounces parallel parallelogram of forces particles passes pendulum perpendicular piece pinion piston placed point of suspension position pounds pressure principal axes principle produce projecting arm proportion pulley quantity of motion radius radius of gyration rectilinear motion rection represented in fig resistance rest revolve rope round screw side space steel steelyard substance suppose surface suspended sustain teeth thread tion tube vibration weight wire zinc
Seite 300 - ... delicacy of touch, which is desirable in such operations. — Kater. Why does one weight alone serve to determine a great variety of others, by the steelyard ? Because the steelyard is a lever, having unequal arms, and by sliding the weight along the longer arm of the lever, we thus vary its distance from the fulcrum, taken in a reverse order ; consequently, when a constant weight is used, and an equilibrium established, by sliding this weight on the longer arm of the lever, the relative weight...
Seite 128 - ... position must be regulated by the centre of gravity of his body and the load taken together. If he bore the load on his back, the line of direction would pass beyond his heels, and he would fall backwards. To bring the centre of gravity over his feet he accordingly leans forward., fig.
Seite 51 - Every body must persevere in its state of rest, or of uniform motion in a straight line, unless it be compelled to change that state by forces impressed upon it.
Seite 334 - ... the distance from the point of suspension to the centre of oscillation must remain the same.
Seite 298 - The weights I use are one globule of gold, which weighs one grain ; and two or three others which weigh one-tenth of a grain each ; and also a number of small rings of fine brass wire made in the manner first mentioned by Mr. Lewis, by appending a weight to the wire, and coiling it with the tension of that weight round a thicker brass wire in a close spiral, after which the extremity of the spiral being tied hard with waxed thread, I put the covered wire in a vice, and applying a sharp knife which...
Seite 222 - In many cases, the utility of the wedge depends on that which is entirely omitted in its theory, viz., the friction which arises between its surface and the substance which it divides. This is the case when pins, bolts, or nails, are used for binding the parts of structures together ; in which case, were it not for the friction, they would recoil from their places, and fail to produce the desired effect. Even when the wedge is used as a mechanical engine, the presence of friction is absolutely indispensable...
Seite 53 - When two bodies moving in opposite directions meet, each body sustains as great a shock as if, being at rest, it had been struck by the other body with the united forces of the two. Thus, if two equal balls, moving at the rate of ten feet in a second, meet, each will be struck with the same force as if, being at rest, the other had moved against it at the rate of twenty feet in a second.
Seite 204 - By means of the fixed pulley a man may raise himself to a considerable height, or descend to any proposed depth. If he be placed in a chair or bucket attached to one end of a rope, which is carried over a fixed pulley, by laying hold of this rope on the other side, as represented in fig.
Seite 56 - ... and is usually expressed thus : " If two forces be represented in quantity and direction by the sides of a parallelogram, an equivalent force will be represented in quantity and direction by its •diagonal.
Seite 33 - When air is violently compressed, it becomes so hot as to ignite cotton and other substances. An ingenious instrument for producing a light for domestic uses has been constructed, consisting of a small cylinder, in which a solid piston moves air-tight : a little tinder, or dry sponge, is attached to the bottom of the piston, which is then violently forced into the cylinder : the air between the bottom of the cylinder and the piston becomes intensely compressed, and evolves so much heat as to light...