Mechanics

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Longman, Rees, Orme, Brown, and Green, 1830 - 342 Seiten
 

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Seite 90 - ... 64 feet per second ; and towards the end of the fall, it would be about 120 feet per second. It is evident that this great degree of rapidity would be a serious impediment to accurate observation, even though we should be able to command the requisite height. It occurred to Mr. George Attwood, a mathematician...
Seite 27 - 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...
Seite 185 - ... indentures of each wheel fall between the corresponding ones of that in which it works, and ensure the action BO long as the strain is not so great as to fracture the tooth.
Seite 123 - ... 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 327 - ... the distance from the point of suspension to the centre of oscillation must remain the same.
Seite 218 - 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 45 - 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 101 - The consideration of centrifugal force proves, that if a body be observed to move in a curvilinear path, some efficient cause must exist which prevents it from flying off, and which compels it to revolve round the center. Thus the bodies of the solar system are constantly impelled or drawn towards the sun by a force which we denominate gravity.
Seite 50 - ... 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 12 - Animalcules have been discovered, whose magnitude is such, that a million of them does not exceed the bulk of a grain of sand ; and yet each of these creatures is composed of members as curiously organized as those of the largest species ; they have life and spontaneous motion, and are endued with sense and instinct.

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