The elements of physiological physics The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology elementsofphysio00mgre Year: 1884 Chap. XLL] PULLEYS, 499 xS\'.\y ••'. \ in the least the result of the movable one. The latter has a hook attached from which a weight is suspended. Now when the rope is pulled with a force of 1 pound, let us say, that force is communi- cated to the hook in the beam. It is a law of dynamics that action and reaction are equal. If the hook is pulled on with a force of 1 pound, it
The elements of physiological physics The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology elementsofphysio00mgre Year: 1884 Chap. XLL] PULLEYS, 499 xS\'.\y ••'. \ in the least the result of the movable one. The latter has a hook attached from which a weight is suspended. Now when the rope is pulled with a force of 1 pound, let us say, that force is communi- cated to the hook in the beam. It is a law of dynamics that action and reaction are equal. If the hook is pulled on with a force of 1 pound, it reacts with a force of 1 pound. Now the force of 1 pound acts in a direction to raise the movable pulley, and the force of reaction acts for the same end. The pulley with its attached weight is thus pulled up- wards with a force of 2 pounds. But the movable pulley does not rise in the same degree that the free end of the rope descends; owing to the doubling of the rope, it is raised by only half the distance. It is also plain that if several movable pulleys were used, connected together, the rope passing from one to the other, and the weight hanging to the sj^stem, the power necessary to raise the weight would be diminished in proportion to the number of pulleys. Such a system of pulleys is shown in Fig. 211. It is to be noted that the height to which the weight is raised with a certain length of rope pulled, smaller and smaller as the of pulleys is increased. A force is capable of raising becomes number smaller w through the weight, but it must act distance. In short, the work done is whether the pulleys be many or few. done is estimated bv the weight raised distance through which it is of 10 pounds raised 1 foot is of 1 pound raised 10 feet. Fig. 211.—A Sys t e m of Movable Pul- leys. a longer the same The work into the weight same as a weight weight raised. Thus a the So that if
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