Volume 1

The elements of natural or experimental philosophy / By Tiberius Cavallo.

  • Cavallo, Tiberius, 1749-1809.
Date:
1803
Catalogue details

Licence: Public Domain Mark

Credit: The elements of natural or experimental philosophy / By Tiberius Cavallo. Source: Wellcome Collection.

    156/412 (page 124)
    It will be hardly ncceflary to obferve, that a ba- lance ol forces may take place amongft any number of tuch forces; fo that a body may remain perfect- ly at reft, though aded upon by four or five, or any other number of forces. In this cafe the forces arc fometimes called prejfures ; for in fad they only prefs upon the body without being able to move it out of its place. V. As the joint a A ion of fever al impulfes compel a body to perform a certain courfe, Jo whenever we ob- ferve any particular courfe of a body, we may imagine * that courfe to be produced by the joint action of two or more impulfes that are equivalent to that fingle im- pulfe. Thus finding that a body A, fig. 26, Plate II. has moved from A to C, we may imagine either that the body has been impelled by a fingle force in the diredion of A C, and proportionate to the length of AC, or that it has been impelled by two forces at once, viz. by one in the diredion of A D, angle A B D, fig. 29, Plate II. A B is to B D as the fme of the angle ADB, or D A C, is to the fine of the angle D AB ; hence any two powers will be to each other reciprocally as the fines of the angles, which the lines re- prefenting their directions, make with the direction of the third power. Farther, AD is to A B as the fine of the angle AB D is to the fine of B DA, or D A C ; and in like manner the power aCting according to A E is to the power aCting according to AC, as the fine of the angle A C D is to the fine of the angle ADC, or B A D. and