The groundwork of practical naval gunnery; a study of the principles and practice of exterior ballistics, as applied to naval gunnery, and of the computation and use of ballistic and range tables . 27 cot R = 10000 log colog -10 h , — COtw —^ = log —— cot O) 1+ —„— = log = yards log 91. We can now make a comparison between the trajectory in vacuum and thatin air for the same initial velocity and angle of departure. Figure 9 represents on the same scale the trajectories in air and in vacuum of a12 projectile weighing 870
The groundwork of practical naval gunnery; a study of the principles and practice of exterior ballistics, as applied to naval gunnery, and of the computation and use of ballistic and range tables . 27 cot R = 10000 log colog -10 h , — COtw —^ = log —— cot O) 1+ —„— = log = yards log 91. We can now make a comparison between the trajectory in vacuum and thatin air for the same initial velocity and angle of departure. Figure 9 represents on the same scale the trajectories in air and in vacuum of a12 projectile weighing 870 pounds, c = , fired with an initial velocity of 2900 f. s.,at an angle of departure of 4° ; the range in vacuum for this angle of departurebeing feet ( yards), and in air of standard density, being 30,000feet or 10,000 yards. In the figure the ordinates of both curves are exaggerated tentimes as compared with the abscissae, in order that the curve may be seen. GENERAL AND APPROXIMATE DEDUCTIONS 63 If gravity did not act, the projectile would move in the tangent to the curveOQ1Q2, and in traveling the horizontal distance x = OA, would rise to the height. A. ^ ^, Figure between Trajectory in Vacuum and that in Air for same and same /. V. AQ^ = x tan = 4° tan y = 14 feet log The attraction of gravity, however, pulls the projectile down QJ^^= -— 9^ 2V^ cos- (^ while it moves OA horizontally, and so for the ordinate of the trajectory in vacuumwe have AP, = y, = ^yS^ We have already computed the value of x tan cj> as above and found it to be Therefore, computing the second term of the right-hand member of the aboveequation, we have 5r = log a; = 20000 log 2 log 2 log colog i; = 2900 2 colog = 4° 2 sec -_2^,_ = feet log 2K^cos-<^ a; tan <^ = feet APj^ = rj^ = x tan -.,- gx~Fcos^ 7
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectballistics, bookyear1
