Volume 183001

Mechanics / By Henry Kater and Dionysius Lardner.

  • Henry Kater
Date:
1830
Catalogue details

Licence: Public Domain Mark

Credit: Mechanics / By Henry Kater and Dionysius Lardner. Source: Wellcome Collection.

    160/408 page 134
    several forces act upon it, the direction of each of them crossing the axis either perpendicularly or obliquely, or taking the direction of the axis or any parallel direction, their effects may be similarly investigated. In the same manner we may determine the effects of any number of forces whose combined results are mechanically equiva- lent to forces which either intersect the axis or are pa- rallel to it. (184.) If any force be applied whose direction lies in a plane cblique to the axis, it can always be resolved into two elements (76.), one of which is parallel to the axis, and the other in a plane perpendicular to it. The effect of the former has been already determined, and therefore we shall at present confine our attention to the latter. Suppose the axis to be perpendicular to the paper, and to pass through the point G, fig. 71., and let A B C be a section of the body. It will be convenient to consider the section vertical and the axis horizontal, omitting, however, any notice of the effect of the weight of the body. ; Let a weight W be suspended by a cord QW from any point Q. This weight will evidently have a tend- ency to turn the body round in the direction A B C, Let another cord be attached to any other point P, and, being carried over a wheel R, let a dish S be attached to it, and let fine sand be poured into this dish until the tendency of S to turn the body round the axis in the direction of C B A balances the opposite tendency of W. Let the weights of W and 8 be then exactly ascertained, and also let the distances GI and G H of the cords from the axis be exactly measured. It will be found that, if the number of ounces in the weight 8 be mul- tiplied by the number of inches in G H, and also the number of ounces in W by the number of inches in GI, equal products will be obtained. ‘This experiment may be varied by varying the position of the wheel R, and thereby changing the direction of the string PR, in which cases it will be always found necessary to vary the weight of S in such a manner, that when the num-
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