Elementary lessons in the physics Elementary lessons in the physics of agriculture elementarylesson01king Year: 1894 40 72. Transverse Strength of Elaterials.—When a board is placed upon edge and fixed at one end as represented at A, Fig. 19, a load acting at W puts the upper edge under a crushing stress. V 'We know from experience that in case the board breaks under its load when so situated the fracture will occur some- where near 5-6. E^ow in order that this may take place, there must be, with white pine, according to 70, a tensile stress at the upper edge of ten thousand pounds to the
Elementary lessons in the physics Elementary lessons in the physics of agriculture elementarylesson01king Year: 1894 40 72. Transverse Strength of Elaterials.—When a board is placed upon edge and fixed at one end as represented at A, Fig. 19, a load acting at W puts the upper edge under a crushing stress. V 'We know from experience that in case the board breaks under its load when so situated the fracture will occur some- where near 5-6. E^ow in order that this may take place, there must be, with white pine, according to 70, a tensile stress at the upper edge of ten thousand pounds to the square inch, and if the board is one inch thick the upper inch should resist a stress of ten thousand pounds at any point from 5 to 1; but we know that no such load will be carried at W. The reason for this, and also for its breaking at 5 rather than at any other point, is found in the fact that the load acts upon a lever arm whose length is the distance from the point of attachment of the load to the breaking point, wherever that may be, and this being true the greatest stress comes necessarily at 5. If the board in question is forty-eight inches long and six inches wide, it will, in breaking, tend to revolve about the center of the line 5-6, and the upper three inches will be put under a longitudinal strain, but according to 70, it is capable of withstanding 3x10,000 ,000 lbs. without breaking; but in carrying the load at the end, as shown, this cohesive power is acting at the short end of a bent lever whose mean length of power-arm is one-half of 4-5 or inches, while the weight-arm is forty-eight inches in length. It should, therefore, only be able to hold at W, pounds; for . asP. xP. xW. A., we have 3,000 x x 48, whence VJ'.-^A^=Q3' lbs.
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