MACHINERY. The utility of machin ery consists in the addition which it makes to human power. The forces de rived from wind, water, and steam, are so many additions to human power, and the total inanimate force thus obtained in Great Britain has been calculated by Dupin to be equal to 20,000,000 laborers. Instead of working himself, man makes nature work for him, and, in that degree, ought to be enabled to live as well, and work less himself. The effect ought, in this respect, to ease the whole commu nity, or it ceases to be an advantage. On the contrivance of every new tool, human labor is abridged. The man who con trived rollers quint spied his power over brute matter. A tool is usually a more simple machine, and generally used by the hand; a machine is a complex tool, a collection of tools, and frequently put in action by inanimate force. All machines are intended either to produce power, or merely to transmit power and execute work. All the mechanical powers are, in effect, levers.
In the wheel and axle, the wheel is the long arm, the axle the short arm, and their ratio or division is the power.
In the pulley, one gives no power, but two gives douole the velocity of the power ; three treble, and so on, exactly on the lever principle.
The inclined plane operates as a lever, because the distance moved on the plane is greater than the height gained; hence, the power is as the length of the plane to the height.
The wedge is another lever, on the same principle as the inclined plane, but varied m power by resistance.
The screw is alever in which the power moves through the entire circumference, while the obstacle moves only through the distance of the threads.
Friction diminishes the results, but, in general, a fourth or fifth more power is applied than the calculation demands, to compensate for friction, and other causes of loss of power.
When two bodies balance each other by means of any machine, and are then made to move, the product of each into its velocity, i. e. the quantities of motion or momentum ascending or descending perpendicularly will be equal.
The quantity of power in motion is the velocity multiplied into the quantity of matter or number of atoms. Thus, a cubic inch of lead, moving 1 yard per has a momentum of 1; and 2 cubic inches a momentum of 2 ; or 1, moved 2 yards, a momentum of 2. But , a cubic inch of stone, but half the density of in yard per second, have I but half the momentum of the lead, and two cubic inches of such stone must move twice as fast as the lead, to have the same force or momentum.
Hence, universally, velocity, bulk, and density, must be multiplied together for momentum ; and, if we diminish one, we must increase one of the two others, or both, to have the same momentum. Animal, or other force, often stands for bulk and density, and then these must be varied as velocity.
As we increase velocity, with the same power we increase momentum ; and, as we decrease velocity, we must increase power, to get an equal momentum.
This is the foundation of all mechanical science and practice, however varied or complicated ; and this principle being un we may, by the aid of common arithmetic, be able to pursue every use ful mechanical object.
It sometimes happens, as in chemistry, that the power is invisible ; but, in these cases, if there is power, it is not the less matter and motion. Invisible atoms are concentrating, or are dispersing, or are moving one among another in such cases. We often understand their action, and sometimes do not ; but our ignorance, in particular cases, creates no alteration in the general laws of nature.
To determine the relative velocity of a body moving in any angle from the direc tion of the moving force, multiply the velocity conferred by the moving force by the natural cosine of the angle, and the product is the velocity in the angular Ai rection. And, to find the perpendicular distance of the two lines, multiply the angular velocity by the sine of the angu lar deflection, and the product is that distance. The relative lengths of the three lines is the measure of the force in each.