FORCE, in mechanical and scientific mat ters, is a term employed to denote the un known cause of any mechanical effect. Thus the cause of motion and the cause of pressure are both forces : again, difference of effects must be attributed to difference in the pro clueing causes : thus, greater or less velocity, and greater or less pressure, are both attri buted to differences in the causes of velocity or pressure. But, on the other hand, effects which are the same in one point of view may differ in another; thus, bodies of different weights, let fall from the same heights above the ground, will strike the ground with the same velocities, but with different degrees of effect upon the substance which they strike.
When force, in the senao of pressure, is considered as the cause of motion, we must take into account both the element time, and also the quantity of matter which is moved. The connection of pressure, velocity created by pressure, and time which pressure takes to create velocity, as deduced from experi ment, are contained in the following results : 1. The same pressure continually acting
upon a given mass for different times pro duces velocities which are proportional to the times, and augments velocity by equal portions in equal times.
2. The same pressure applied to different masses of matter (that is to different weights of matter), during the same time, produces velocities which are inversely proportional to those masses.
3. The velocities of falling bodies is accele rated by 32.19 feet in every second: and in that proportion for all other times.
Very exact calculations and experiments on all these points are of great importance to machinists and engineers, who have to pro vide force adequate to the kind and quantity of the work to be done.