POWER, in mechanics, denotes any force, whether of a man, a horse, a spring, the wind, water, &c. which being applied to a machine, tends to produce motion.
The intensity of a power is its absolute force ; that is, its force, supposing its ve locity equal to its weight : for its moving or acting force maybe greater or less, ac cording as its velocity is increased or di minished, in respect of that of the weight. As, for example, if a man be the power, and can raise from the ground a certain weight, that weight will express or be equal to the intensity of the power ; for in this case, whatever engine be made lise of that part of the engine, where the weight is duly applied, will move just as fast as that on which a man acts with his whole force. A power may act in any direction whatever ; but a weight has only one direction, viz. towards the cen tre of the earth.
When we speak of the mechanical powers, the word power is taken in a ve ry different sense from that above laid down ; since, in this case, it signifies only an organ or instrument, whereby a power of a known intensity is made to act upon a weight; and, therefore, we must take care not to attribute any real force to any simple or compound machine, as many are apt to do, merely because the name power has been given to mechanical or gans, not from their effect, but from the effect which the power produces by their means. For how much soever the force
of a power is thereby increased, in order to sustain or raise a weight far superior to it in intensity, yet this cannot be done without losing in space and time what is gained in force ; contrary to what some have vainly imagined, because the vulgar commonly speak of a machine as they do of an animal ; attributing that effect to the machine, which is only the effect of the power by means of the machine : thus, it is usual to say, such a machine raises such a quantity of water, or performs such and such work ; when we should say, if we would speak philosophically, such a run ning stream, such a fill of water, the wind, or so many men, horses, oxen, &c. raise so much water in such a time, &c. by means of such or such a Machine. It were, therefore, to be wished, that the word power were to be confined to its proper sense, and not used to signify one of the mechanical organs ; however, as it has been customary to use it in that sense, we have done so too, but have neverthe less thought proper to gi ve the above cau tion. See MECRANICS.