PRINCIPLES OP GUNNERY. 
265 
The velocity at P being known, it is easy to find the velocity at B 
(200 ft. distant) thus : 
S 
S 0 : = Sr, + - S = /Vu + *6045 X 200 
io 
so that 
= 3455-2 + 120*9 = 3576-1; 
velocity at B or v' = 1051 f.s. 
Now the time over PB can be found thus : 
T 
J-v 
T - 
T = Xv 
^05i"^i064 _ 2-7328 - 2-6182 
•6045 
-6045 
= T9 sec. 
Put i! for the time over PB, then 
t' = -19 sec. 
But time over OP = t — 3‘2 secs.; so that from equation (6), 
X 3-2 x -19= 9-79 ft. 
PN = £ W— — 
2 2 
i.e., the vertical distance below the crest of the traverse that the shell 
will strike an escarp 200 ft. beyond is 9*79 ft. 
The approximate angle of descent at the escarp may be also found. Angie of 
If 6 is the angle of descent at the escarp, 
, . vertical velocity r77i ., 
tan A = . . - - -r— . ride equation (7), p. 263 i. 
horizontal velocity • 
But if T be the whole time of flight, and the vertical motion be treated 
as for an unresisted projectile, 
vertical velocity 
2 ’ 
and horizontal velocity on impact is found from equation 
so that 
T V = T V + T, 
w 
q total time of flight 
tan d) = d . ___ _ . mi ; 
2 horizontal velocity on impact 
or approximately for small angles, 
180 ff total time of flight 
p = 
7r 2 horizontal velocity on impact 
In the above case, 
P= t + t'z=z 3-2 + -19 = 3-39 secs., 
3-39 
so that 
32-2 
2 
or </>=2° 58'. 
tail <l> — =- X =- ='03192; 
