Mechanics. 1st (-3rd) year1878 |
Kluczowe wyrazy i wyrażenia
act at right applied attraction axis balance ball base body centre of gravity centrifugal force centripetal force circumference cohesion cold cord diameter direction distance earth elasticity employed equal equilibrium EXERCISES expansion feet find the centre fixed pulley fly-wheel force of gravity forces acting friction fulcrum gases greater heat heavy horizontal inches inclined plane instance iron joint effect ladder law of motion length liquid longer arm lower block mangling machine mass matter means measured mechanical advantage metal move moveable pulleys opposite P's arm parallel forces parallelogram Parallelogram of Forces particles pendulum piston placed pressure pulling pump radius raised resistance resultant revolve right angles rope round scale pan screw second kind shorter arm side simple machines solid specific gravity square steam straight line system of pulleys toothed wheel triangle varies velocity vertical wedge weight wheel and axle
Popularne fragmenty
Strona 121 - ... but, on the other hand, they are free from the friction of the rollers with the under surface of the load, or the carriage in which the load is transported. The advantage of wheel carriages in diminishing the effects of friction, is sometimes attributed to the slowness with which the axle moves within the box, compared with the rate at which the wheel moves over the road ; but this is erroneous. The quantity of friction does not in any case vary considerably with the velocity of the motion, but...
Strona 109 - PULLEYS. la entirely maintained by the frictional adhesion between them, it may happen that it may occasionally fail through the band sliding on the pulley. This, if not excessive, is an advantageous property of the contrivance, because it enables the machinery to give way when unusual obstructions or resistances are opposed to it, and so prevents breakage and accident. For example, if the pulley to which motion is communicated were to be suddenly stopped, the driving pulley, instead of receiving...
Strona 116 - In the steam-engine the self-regulating principle is carried to an astonishing pitch of perfection. The machine itself raises in a due quantity the cold water necessary to condense the steam. It pumps off the hot water produced by the steam, which has been cooled, and lodges it in a reservoir for the supply of the boiler. It carries from this reservoir exactly that quantity of water which is necessary to supply the wants of the boiler, and lodges it therein according as it is required. It breathes...
Strona 40 - When a force acts upon a body in motion, the change produced in the quantity of motion is the same, both in magnitude and direction, as if the force acted on the body at rest. The...
Strona 16 - ... while speculating upon apparently remote phenomena. You cannot enter a quarry and scrutinise the texture of the rocks without seeing that it is not perfectly homogeneous. If the quarry be of granite, you find the rocks to be an agglomeration of crystals of quartz, mica, and felspar. If the rocks be sedimentary, you find them, for the most part, composed of crystalline particles derived from older rocks. If the quarry be marble, you find the fracture of the rocks to be what is called crystalline...
Strona 58 - the sun's rays are the ultimate source of almost every motion which takes place on the surface of the earth. By its heat are produced all winds, and those disturbances in the electric equilibrium of the atmosphere which give rise to the phenomena of lightning, and probably also to those of terrestrial magnetism and the aurora.
Strona 109 - But if motion is to be transmitted in an exact proportion, for example, such as is required in clock-work, where the hour hand must make one exact revolution while the minute-hand revolves exactly 12 times, bands are inapplicable ; for supposing it practicable to make the pulleys in so precise a manner that their diameters should bear the exact proportion required, which it is not, this liability to slip would be fatal. But in all that large class of machinery in which an exact ratio is not required...
Strona 121 - The wheels of carriages may be regarded as rollers which are continually carried forward with the load. In addition to the friction of the rolling motion on the road, they have, it is true, the friction of the axle in the nave ; but, on the other hand, they are free from the friction of the rollers with the under surface of the load, or the carriage in which the load is transported. The advantage of wheel carriages in diminishing the effects of friction, is sometimes attributed to the slowness with...
Strona 16 - ... upon apparently remote phenomena. You cannot enter a quarry and scrutinise the texture of the rocks without seeing that it is not perfectly homogeneous. If the quarry be of granite, you find the rocks to be an agglomeration of crystals, of quartz, mica, and felspar. If the rocks be sedimentary, you find them, for the most part, composed of crystalline particles derived from older rocks. If the quarry be marble, you find the fracture of the rocks to be what is called crystalline fracture. These...
Strona 47 - ... to the second ; the second to the third; the third to the fourth ; and so on : Silver, Copper, Iron, Tin, Lead, Zinc.