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LEFT FORCE PUMP 171 FORD work as any other. It has long been known that in a machine, the screw for example, what is gained in power is lost in velocity, and vice versa. At first sight motion and heat seem to have no relation to each other; but if a moving body be suddenly arrested in its career, as, for instance, a bullet by a target, heat will be generated, and the same number of units of the work which the motion was capable of effecting can be achieved also by the heat. Conversely, a certain amount of heat can produce an equivalent one of motion; thus the working energy communicated to the piston of a steam engine is withdrawn from the heat of the steam, and exactly balances the latter. By equilibrium of forces is meant the action of forces which, balancing each other, produce an equilibrium or state of balance, or rest in the body or bodies on which they operate. An impulsive force is a force which acts on a body for an unappreciably short time, as when one body strikes another. Kinetic force is the actual force excited by a moving body as distinguished from the potential forces which it is capable of creating. Potential force is the whole force which a body in motion can exert, as distinguished from the kinetic force which it is exerting at the specific mo- ment of time. The measure of force is the measurement of the magnitude of a force, which is done by noting the mo- mentum which it communicates to a body in a unit of time. The unit of force is the force which acting on a pound mass would, in one second, produce a velocity of a foot per second. Mechan- ical force is force of a mechanical na- ture acting on material bodies. It may be either that of the active force of a body in motion, or the tension or resist- ance opposed by a body at rest. Molecu- lar forces are those which by means of certain attractions and repulsions retain the atoms of matter side by side without their touching each other. When a force tends to produce rotation about a fixed point the tendency is called Moment. FORCE PUMP, a pump which delivers the water under pressure, so as to eject it forcibly or deliver it at an elevation. The term is used in contradistinction to a lift pump, in which the water is lifted, and simply runs out of the spout. The single-acting force pump is that in which the lift and delivery are alternate. The double-acting is that in which the pas- sages are duplicated, so that a lift and delivery are obtained by each motion of the plunger; the pump has a distinct water-way both above and below the pis- ton, so as both to draw and force water at each stroke, and thus cause a continu- ous stream, which is rendered more uni- form by an air-chamber. Also the boiler- supply pump sometimes connected to the piston rod of the cylinder of a loco- motive. FORD CITY, a borough in Pennsyl- vania, in Armstrong co. It is the center of an important agricultural and coal- mining region and its industries include the manufacture of plate glass. Pop. (1910) 4,850; (1920) 5,605. FORD, HENRY, an American cap- italist and philanthropist, born at Green- field, Mich., in 1863. After attending a district school he learned the machinist's trade and moved to Detroit to secure em- ployment. After securing notable suc- HENRY FORD cesses in his vocation he became chief engineer of the Edison Illuminating Co. and in 1903 organized the Ford Motor Co., which became the largest automobile company in the world. In the conduct of his plant he achieved great success partly by his enlightened attitude toward his employees, granting them high wages, making them profit-sharers in the plant, and maintaining for their benefit hospitals and schools. In 1915 he financed a group of peace advocates which attempted to influence the belli- gerent powers to end the World War. After the war he was among the first