Articoli correlati a Compilation of the papers on physics
Sinossi
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1877 Excerpt: ...nearly on a straight line, as is shown by column 5, which gives values of log t, computed by the for mula G = £ log I-j-.75. The close agreement shows that t = m /l, or that the time is proportional to the square root of the length. 2. Force of Magnetism. The observations given in Table II. were made by Professor Mayer (Amer. Jour. Sci., Sept. 1870), to determine the effect of a coil on a galvanometer needle placed at different distances. TABLE II. The first column gives the distance, the second its logarithm, and the third the logarithm of the force produced, or the tangent of the angle of deflection. To see if f=m dn, a curve was constructed, with columns 2 and 3 as co-ordinates, and appeared to coincide very closely with the line y =--2.76 x--2.545. Column 4 gives the values of log f thus computed, which shows a close agreement with observation. The result found by Professor Mayer was n = 2.7404; but the last two figures should be omitted, as they alter the result by only about one or two hundredths as much as the accidental errors. 3. Resistance of Air. Another excellent example is found in the resistance of air to projectiles. Newton assumed that the resistance was proportional to the square of the velocity, or R = m v1; but this result is not sustained experimentally. The agreement with the cube of the velocity is, in fact, more exact; but neither is the true law. A more careful examination shows that the law alters for velocities above and below that of sound, or about 1,100 feet per second; since above that velocity the air cannot flow in rapidly enough to fill the space behind the shot, but leaves a vacuum. To show this, a series of observations with the Bashforth chronograph were examined, and showed in a marked manner the change when f = 1,1...
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