DYNAMICS* 49 



SECT. V. 



MQTION QF PliQJECTILES. 



rj.fi -.:.",] bl. 



93, AF a heavy body be projected in the direction 

 of a straight line, not perpendicular to the horizon, 

 it >vijl describe a parabpla situate in the vertical 

 plane passing tjirough that straight line, and ha- 

 ving its axis perpendicular to the horizon. 



a. For it advances in the line of projection at a uni- 

 form rate, and descends below it with a velocity uni- 

 formly accelerated. 



b. The straight line in the direction of which the body 

 is projected, touches the parabola in the point of pro- 

 jection. 



c. Gravity is here supposed to have its intensity and 

 its direction the same at all points, within the range 

 of the same projectile. We also abstract from the 

 resistance of the air. 



4. This proposition "was discovered by GALILEO, and 

 demonstrated, J)ialogo iv. de fyfotu Projectorum. 



94. If from the poiijt of projection there be ta- 

 ken upwards, in a vertical line, a part equal to 



, (c being the velocity with which the body is 

 VOL. i. i> projected.) 



