. The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology. Biophysics. 496 PH YSIOL OGJCA L PH YSICS. [Chap. the the longer than the resistance, and has consequently always the advantage. It is the lever of power, though, as in the first order, the power must always move through a greater distance than the weight. The third order of levers is shown in Fig. 206. The power is between the weight and fulcrum. Here weight has a arm than the power. Let w be distant 4 feet Fig. 206.—Lever of Third Order.
. The elements of physiological physics: an outline of the elementary facts, principles, and methods of physics; and their applications in physiology. Biophysics. 496 PH YSIOL OGJCA L PH YSICS. [Chap. the the longer than the resistance, and has consequently always the advantage. It is the lever of power, though, as in the first order, the power must always move through a greater distance than the weight. The third order of levers is shown in Fig. 206. The power is between the weight and fulcrum. Here weight has a arm than the power. Let w be distant 4 feet Fig. 206.—Lever of Third Order. » n ,, irom F, and p 2 feet, and let w = 10. The moment of w is 40. Acting o through 2 feet a power of 20 is necessary to yield the same moment. Therefore, with these distances the power must be more than double the weight to raise it. Here, therefore, the weight has the advantage. But it is evident from Fig. 207 that the weight moves through a much greater distance (from w to w') than the power (from p to P'). A small movement of the power will, therefore, give a good sweep of the weight. This lever is, therefore, a lever of velocity ; the weight passes over a con- siderable distance in a short time. We shall see, in the chapter on Animal Mechanics, (chap, xliii.) how the muscles, bones, and joints of the body can be classified under such a system of levers. The balance is another illustration of the prin- ciples applicable to parallel forces. This is particu- larly well shown in the Danish balance (Fig. 208). It consists of a steel arm with a fixed weight P at one end. At the other end is a hook carrying a scale pan. The arm is supported a beam resting on the edge of the ring-shaped oody F, which is the. 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. Ph
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