
52 Ballistics: Theory and Design of Guns and Ammunition
We shall now examine the use of momentum, mV, as our ow variable. Use of Equation
2.128 with this ow variable yields
== =
V
(2.135)
Now we can include this into Equation 2.129 to obtain
d
dV
dd
CV outflow area inflow area
m
tt
VVVA VV A
=
∂
+⋅
∫∫ ∫
ρρ ρ
(2.136)
Through Newton’s second law, we know that the term on the LHS (time rate of change of
momentum) equals the forces on the system. The rst term on the RHS is the change in
the system’s momentum through storage in the CV. The second and third terms are the
momentum leaving and momentum entering the CV, respectively. It is again i