Sir I s a a c N e w t o n’s Book I.

3 °

acted upon by any power, yields to that power, moving inthe fame line, in which the power applied is directed ; andmoves with a less or greater degree of velocity, according tothe degree of the power ; so that twice the power shall com-municate a double velocity, and three times the power athreefold velocity. If the body be moving, and die powerimpressed act upon the body in the direction of its motion,the body shall receive an addition to its motion, as great asthe motion, into which that power would have put it from astate of rest; but if the power impressed upon a moving bo-dy act directly opposite to its former motion, that power shallthen take away from the body’s motion, as much as in the ci-ther cafe it would have added to it. Lastly, if the power beimpressed obliquely, there will arise an oblique motion dif-fering more or less from the former direction, according asthe new impression is greater or less. For example, if the bo-dy A (in fig. I.) be moving in the direction A B, and when it isat the point A, a power be impressed upon it in the directionA C, the body shall from henceforth neither move in its firstdirection A B, nor in the direction of the adventitious power,but shall take a course as A D between them : and if thepower last impressed be just equal to that, which first gaveto the body its motion ; the line A D shall pass in the middlebetween A B and A C, dividing the angle under BAC intotwo equal parts; but if the power last impressed be greaterthan the first, the line AD shall incline most to AC ; whereasif the last impression be less than the first, the line A D shallincline most to A B. To be more particular, the situation of

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