Voiv. 6, 1920 
PHYSICS: A. G. WEBSTER 
653 
Then we have 
P = 
RTcoz 
+ Sx - co(l - z)/8 
cozrj 
(6) 
In order to write the dynamical equation of motion of the shot we shall 
assume that the resistance of the rifling (sometimes known as the passive 
resistance) which is due to the friction of the shot against the lands, and 
would naturally contain a term proportional to the pressure, is a linear 
function of the pressure 
R = Ro -\- bp. (7) 
If then m is the mass of the shot, u its velocity, t the time, and if we take 
account of the inertia of the gas already formed, which is really coz, by 
means of a factor X, we have 
^ = u, (8) (m + \co)^ = S{p - p.) - Ro - bp, (9) 
at at 
where po is the atmospheric pressure, which is so small that it may gener- 
ally be neglected. 
By integration of (9) with respect to the time, 
(m -f \cc)u = {S - b)Jpdt - {Spo +Ro)t, 
(10) 
