Supplement to the first edition of ... elements of physics, or natural philosophy / [Neil Arnott].

  • Arnott, Neil, 1788-1874
Date:
1828
Catalogue details

Licence: Public Domain Mark

Credit: Supplement to the first edition of ... elements of physics, or natural philosophy / [Neil Arnott]. Source: Wellcome Collection.

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    cannot be entered upon in this elementary work. In very many cases there is a great waste or unavoidable loss of force, because the resistance in yielding runs away or escapes from the force, as when a ship runs away from the wind which is driving her, or the floats of a quick moving water-wheel from the stream which turns it. Horses drawing boats or carriages at the rate of five miles an hour, may exert great force; but with a speed beyond tw'elve miles, nearly their whole effort is required to move their own bodies. As a general rule, although equal quantities of force balance each other when applied to parts of a lever or wheel altogether or nearly at rest, still when force is made to act near an axis or fulcrum, to produce considerable velocity in a more distant part, much of it is wasted in prejssure against the fixed fulcrum. At page 143, after line 2Qtli. A projecting rod or plank or branch of a tree, w’ith a scale attached to it, might thus be made to answer the purpose of a weighing-beam, by observing minutely how far a certain substance, attached to it, bent it, and then trying what w'cights would bend it as much. At page 175, after line ^th. It is true also, that a small wheel will sink to the bottom of a hole, where a larger one would rest on the edges as a bridge. It is not true, however, according to the popular prejudice, that the large hind-wheels of coaches and waggons help to push on the little wheels before them: fore-wheels are made smaller, merely to facilitate the turning of the carriage. At ]>age 176, line \0th froin bottoni{*p. 178). When wheels, instead of standing upright, like a and c shewn here, are made to incline outwards, as is common, owing to the ends of the axle-tree being bent down a little, to give a security against the accident of the wheels falling off, the [)ull to the horses in deep or sandy roads is much