Natural Philosophy. Treatise 2

Natural Philosophy. Treatise 2

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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. 1859 edition. Excerpt: the example in art. 125 gives the weight that might be suspended from the end of the beam, supposing it had no weight of its own; therefore, to find the weight that in practice could be attached at the end of the beam, we must subtract from the answer found as above, half the weight of the beam itself. The weight of the beam in art. 125 would be about 88 lbs.; so that the weight that the beam would bear in addition to this is 7663--44, or 7619 lbs. 128. The most frequent case of transverse strain is that of a beam resting freely on supports at the two ends, with a weight or weights pressing somewhere between. If the weight rests on the middle point, as in fig. 58, each of the supports sustains a pressure equal to A W. We may therefore consider the reaction of B either of the supports, B, as a force acting upwards, and tending to break the beam at C, while the two forces at A and C merely hold the end of the beam fixed, as the wall H-68-does in fig. 56. The moment of the force of rupture is thus W x CB = i W x i AB = i W x AB. But if the beam were fixed in a wall at A, with a force W acting at B, the moment would be W x AB. That is, a beam supported freely at both ends will support four times as much weight at its middle point, as it would if fixed at one end, with the weight resting on the other. Ex. A bar of cast-iron, 2 inches square and 15 feet long, is supported at both ends, what weight applied at its middle will break it? Such a bar, if fixed and loaded as in fig. 56, would support, by the former rule, 8100 x 2 x 22-=-180 = 360 lbs. The breaking-weight in the present case is, therefore, 360 x 4 = 1440 lbs. 129. If a beam supported at both ends is loaded uniformly, the weight supported is twice as great as when more

Product details

  • Paperback | 34 pages
  • 189 x 246 x 2mm | 82g
  • United States
  • English
  • black & white illustrations
  • 1236918746
  • 9781236918741