. The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology. Biophysics. Fig. 209.—The Single Pulley. PHYSIOLOGICAL PHYSICS. [Chap. XLI. if the two forces are to be in equilibrium, so that the pulley is not turned, the two forces must be equal. A small power will not, therefore, raise a larger weight. The advantage of the single fixed pulley is that it alters the direction of the force. Thus, a man wishing to raise a load from the ground may do so by placing himself above the load and pul- ling it upwards
. The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology. Biophysics. Fig. 209.—The Single Pulley. PHYSIOLOGICAL PHYSICS. [Chap. XLI. if the two forces are to be in equilibrium, so that the pulley is not turned, the two forces must be equal. A small power will not, therefore, raise a larger weight. The advantage of the single fixed pulley is that it alters the direction of the force. Thus, a man wishing to raise a load from the ground may do so by placing himself above the load and pul- ling it upwards ; by using a pulley, however, he pulls down- wards, and thus is able to add the weight of his body to the power. Similarly in Fig. 209 the load P (of moment PX BC) requires an equal weight R on the other side of the large pulley to counterpoise it. The single fixed pulley is used in the body for altering the direction of a force. Thus the digastric muscle and the oblique muscles of the eye have the direction of their action changed by bands of fibrous tissue, , acting the part of pulleys. It is, however, otherwise with the movable pulley represented in Fig. 210. Here we have a rope, fixed by a hook to a beam, passing down- wards round a movable pulley, and then upwards. It next passes over a fixed pulley, and its free end has a weight at- tached. The fixed pulley is placed merely for changing the direction of pull, it being incon- venient to pull on the free end of the rope after it has passed round the movable pulley. But. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original M'Gregor-Robertson, J. (Joseph), 1858-1925. Philadelphia, H. C. Lea's son & co.
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