THE MECHANICAL PRINCIPLES OF ENGINEERINF AND ARCHITECTURE

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مقاطع مشهورة

الصفحة 125 - When no unguent is interposed, the friction of any two surfaces (whether of quiescence or of motion) is directly proportional to the force with which they are pressed perpendicularly together ; so that for any two given surfaces of contact there is a constant ratio of the friction to the perpendicular pressure of the one surface upon the other.
الصفحة 126 - The coefficient for the unguent tallow is the same, except in that of metals upon metals. This unguent appears to be less suited for metallic surfaces than the others, and gives for the mean value of its coefficient under the same circumstances -10.
الصفحة 126 - VIII, leads to the following remarkable conclusion, easily fixing itself in the memory, that with the unguents, hogs* lard and olive oil interposed in a continuous stratum between them, surfaces of wood on metal, wood on wood, metal on wood, and metal on metal, when in motion, have all of them very nearly the same co-efficient of friction, the value of that co-efficient being in all cases included between 0,07 and 0,08, and the limiting angle of resistance therefore between 4° and 4° 35'.
الصفحة 377 - STONES.* A STRUCTURE may yield, under the pressures to which it is subjected, either by the slipping of certain of its surfaces of contact upon one another, or by their turning over upon the edges of one another ; and these two conditions involve the whole question of its stability.
الصفحة vii - Moral State and Moral Prospects of Society, being the substance of a course of lectures delivered to the students of the Theological Hall in Edinburgh, — " We know," says this distinguished philosopher, " that there is a mighty force of sentiment and natural affection arrayed against the law of primogeniture But here is the way in which we would appease these feelings, and make compensation for the violence done...
الصفحة 37 - ... of the cylinder. Or it may be conceived to be generated by the motion of a circle, in a direction perpendicular to its surface, and always parallel to itself. 61. A cylinder is either right or oblique, as the axis is perpendicular to the base or inclined. 62. Every section of a right cylinder taken at right-angles to its axis, is a circle ; and every section taken across...
الصفحة 127 - ... than the others, and gives for the mean value of its coefficient under the same circumstances -10. Hence it is evident that where the extent of the surface sustaining a given . pressure is so great as to make the pressure less than that which corresponds to a state of perfect separation, this greater extent of surface tends to increase the friction by reason of that adhesiveness of the unguent, dependent upon its greater or less viscosity, whose effect is proportional to the extent of the surfaces...
الصفحة 526 - ... the strongest form of section is obtained. " The details of these experiments are found in the following Table : — " In the first five experiments, each beam broke by tearing asunder of the lower flange. The distribution by which both were about to yield together, that is, the strongest distribution, was not therefore up to that period reached. At length, however, in the last experiment, the beam yielded by the compression of the upper flange. In this experiment, therefore, the upper flange...
الصفحة 704 - THE FRUITS AND FRUIT TREES OF AMERICA, Or, the Culture, Propagation, and Management in the Garden and Orchard of Fruit Trees generally; with descriptions of all the finest varieties of fruit, native and foreign, cultivated in this country.
الصفحة 8 - The sum of the moments of a number of coplanar forces round any point is equal to the moment of their resultant about that point. Let P and Q be two forces.

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