Elements of Natural Philosophy: A Text-book for High Schools and Academies

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Sheldon, 1885 - 598 páginas
 

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Página 160 - The BAROSCOPE consists of a beam like that of a balance, from one extremity of which is suspended a hollow sphere of copper, and from the other extremity a solid sphere of lead. These are made to balance each other in the atmosphere. If the instrument be placed under the receiver of an air-pump and the air exhausted, the copper sphere will descend.
Página 89 - A lever will be in equiv 1 * v ife s 2% 1% librium when the sum of the moments of the forces tending to turn the lever in one direction is equal to the sum of the moments of the forces tending to turn the lever in the other direction.
Página 486 - Fls- 258' called the principal axis of the mirror. A concave mirror may be considered as made up of an infinite number of small plane surfaces. All radii of the mirror, as CA, CG, and CB, are perpendicular to the small planes which they strike.
Página 549 - ... the plunge of the torrent is suddenly arrested ; in the warmth of the machinery turned by the river; in the spark from the millstone ; beneath the crusher of the miner ; in the Alpine saw-mill ; in the milk-churn of the chalet ; in the supports of the cradle in which the mountaineer, by water-power, rocks his baby to sleep.
Página 461 - The amount of heat thus developed would be equal to that derived from the combustion of fourteen globes of coal, each equal to the earth in magnitude. And if> after the stoppage of its...
Página 243 - Oxygen and hydrogen combine in the proportion of one volume of the former, to two of the latter, to form water.
Página 46 - Below the surface, the wttght decreases as the distance to the center decreases. Above the surface, the weight decreases as the square of the distance increases. ILLUSTRATION. — If the earth's radius is 4,000 miles, a body that weighs 100 pounds at the surface will weigh nothing at the center, since it is attracted in every direction with equal force. At 1,000 miles from the center it will weigh 25 pounds, since 4,000 : 1,000 = 100 : 25.
Página 490 - ... will give the conjugate focus Fig. 639.— Formation of Image. corresponding to any other point of the object; b, for example,1 is the focus conjugate to B. Points of the object lying between A and B will have their conjugate foci between a and b. An eye placed behind the object AB will accordingly receive the same impression from the reflected rays as if the image ab were a real object. 711. Size of Image. — As regards the comparative sizes of object and image, it is obvious, from similar...
Página 42 - The angle between the direction of the moving body after striking and the perpendicular, is called the angle of reflection. The angle of incidence is equal to the angle of reflection, and lies in the same plane.
Página 324 - ... unit difference of potential exists between two points when it requires the expenditure of one erg of work to bring a unit of -)- electricity from one point to the other against the electric force.

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