. A text book of physics, for the use of students of science and engineering . 607). The reason is that the air is movingin and out of the pipe rapidly, and so sets the paperin vibration. In either of these cases, or in the case of a vibratingstretched string, the motion may be felt by placing the finger upon the body. In the case of the fork, or the string, this will quickly bring the body to rest, with cessation of the sound. Fig. 607.—Motion of airin a soundingorgan pipe. 664 SOUND CHAP. Simple harmonic motion.—In the case of all continuous sounds,as apart from a mere explosion, or a blow,
. A text book of physics, for the use of students of science and engineering . 607). The reason is that the air is movingin and out of the pipe rapidly, and so sets the paperin vibration. In either of these cases, or in the case of a vibratingstretched string, the motion may be felt by placing the finger upon the body. In the case of the fork, or the string, this will quickly bring the body to rest, with cessation of the sound. Fig. 607.—Motion of airin a soundingorgan pipe. 664 SOUND CHAP. Simple harmonic motion.—In the case of all continuous sounds,as apart from a mere explosion, or a blow, the source of sound isin a state of vibration. Most vibrating bodies, unless their motionbe very great, execute a simple harmonic motion (p. 220), or theirvibration consists of a combination of simple harmonic it is very important to understand the nature of simple har-monic motion, and the student is advised to read carefully pages220 to 226. There are several points in connection with simple harmonicmotion that may with advantage be recapitulated FlG. 608.—Diagram to represent simple harmonic motion. Thus, if the vector OA rotates with uniform angular velocity abouta point O (Fig. 608) its projection upon any fixed line, say OE,represents a simple harmonic motion. At the instant given, thevector is in the position OA, making angle 6, with OC. ThenBO=AC=OA sin 6. If OA is in the position OF at time t=0, andthe angular velocity of rotation of OA be w, then 6 = wt. Also, if OA be called the amplitude a, and OB = y, y = a sin wt. A simple harmonic motion may also be represented by a curveoabclmn, where the abscissae are times, measured in seconds, and theordinates are the displacements y. Thus the point o corresponds to the instant at which A is at F ;b to that at which A is at E, and so on. The curve obelm, correspondsto one complete rotation of OA. After this the curve repeats itself. Amplitude and frequency.—A body capable of vibration, whendisturb
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