Page:Elementary Text-book of Physics (Anthony, 1897).djvu/24



10. It is an obvious fact of Nature that material bodies move from one place to another, and that their motions are effected at different rates and in different manners. Continued experience has shown that these motions are independent of many of the characteristics of the bodies; they depend on the arrangement and condition of surrounding bodies, and on the fundamental property of matter, called inertia. The science of Mechanics treats of the motions here referred to, and in a wider sense of those phenomena presented by bodies which depend more or less directly upon their masses.

The general subject of Mechanics is usually divided, in extended treatises, into two topics,—Kinematics and Dynamics. In the first are developed, by purely mathematical methods, the laws of motion considered m the abstract, independent of any causes producing it, and of any substance in which it inheres; in the second these mathematical relations are extended and applied, by the aid of a few inductions drawn from universal experience, to the explanation of the motions of bodies, and the discussion of the interactions which are the occasion of those motions.

For convenience, the subject of Dynamics is further divided into Statics, which treats of forces as maintaining bodies in equilibrium and at rest, and Kinetics, which treats of forces as setting bodies in motion. Rh