Practical Acoustics

Practical Acoustics

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1897 edition. Excerpt: ...of the instrument as compared with the kaleidophone in which the lengths are constant. FlQ-4S Any wire clamped at one end and plucked aside goes through a similar series of motions, for there is always a plane of maximum and one of minimum flexural rigidity which work upon it in the way just described, but without some such device it gives only one figure. Experiment LXXX Blackburn-s Pendulum The apparatus shown in Fig. 40 can easily be converted into a compound or Blackburn-s pendulum by sliding a small ring, r, up the cord, so as to make it of a Y-shape (Fig. 49). The height of the bob will now require adjusting by means of the peg. The disc is drawn aside and fastened to an upright D by a thread which is burnt at the proper moment: this plan prevents any wobbling which might otherwise take place. Sand is poured into the funnel as before, but it now describes a compound curve, derived from two harmonic motions at right angles. One of these, that parallel to the plane of the frame, is of the same amplitude and period as if the weight had been displaced from its position of rest in this direction, while the angle of the cord remained stationary in a vertical plane; the other, at right angles to the frame, is executed by the entire length, reckoning from the middle of the under side of the crossbar to the weight. If we wish to obtain the curve combining harmonic motion of periods 1: 2, we put the ring f of the way down, counting from the top; and if the combination 2: 3, at-f, and so on. The reason for this depends on the formula for a simple pendulum, t = irA/-, where = the time of a single oscilla tion in seconds, Z = the length, and g the acceleration of gravity. The times are therefore directly as the square roots of the lengths, or...
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Product details

  • Paperback | 48 pages
  • 189 x 246 x 3mm | 104g
  • United States
  • English
  • black & white illustrations
  • 1236982266
  • 9781236982261