376 



WEBSTER— BALLISTICS OF A GUN 



The method of calculation is as follows : The first approximation 

 by successive arcs indicated by Gen. Siacci is used. The distance 

 of 120 kilometers is divided into twelve equal parts, and the chord 

 is drawn, making use of the velocity obtained, at the end of the 

 preceding chord. We make use of the familiar equations ot 

 ballistics, 

 (2) ds = pd9, 



(3) 

 (4) 

 (5) 



V = 



ds 

 dt' 



an = V-/P = — g COS d, 



dvx 



-di^-'-^^'^' 



in the last of which, which is the only dynamical equation involved, 

 we put 



vdd d{v cos 6) c 



(6) 



dt^ - 



vf{v). 



gcosd' d9 



Instead of differentials we use finite differences. The table shows 

 the computation required for Curve 2, Fig. 4. 



•MASS = 300 KG. JNITIAL VELOCITY- 1300 - 



Oo="' ,2.i<=l'8 SEC. APPROX 



The meaning of the symbols is as follows : 



