Motion of a Spinning Projectile. 



347 



31. In the following table the values of 7 calculated from 

 equations (33), (34), (35), and (36) are put side by side 

 with the values from the • Musketry Regulations/ Of the 

 pair of values given in one column at 600 yards range, one 

 is calculated from (35) and the other from (36). A similar 

 remark explains the pair of values at 700 yards in another 

 column. 





Mark VI. 



Mark VII. 



Eange 



7 



r 



7 



7 



in yards. 



(Musk. Regs.). 



(calculated). 



(Musk. Kegs.). 



(calculated). 



200 



° 2-0 



/ 

 20 



~ ' 

 80 



/ 

 8-02 



300 



7-5 



7-5 



11-3 



11-30 



400 



14-0 



140 



15-3 



15-26 



500 



21-5 



21-5 



202 



20-16 



600 



300 



30-6', 32-5' 



25-9 



26-22 



700 



39-5 



403 



32-7 



33-72', 354' 



800 



50-0 



50-3 



40-5 



41-7 



900 



1 20 



1 2-0 



49-6 



50-0 



1000 



1 15-5 



1 153 



1 01 



1 0-2 



1100 



1 30-5 



1 30-3 



1 121 



1 12-1 



1200 



1 47-0 



1 46-7 



1 25-7 



1 25-7 



1300 



2 5-0 



2 4-8 



1 41-1 



1 41-2 



1400 



2 24-5 



2 24-5 



1 58-4 



1 58-6 



1500 



2 46-0 



2 45-9 



2 17-8 



2 18-0 



1600 



3 9-5 



3 92 



2 395 



2 39-6 



1700 



3 350 



3 34'4 



3 3-5 



3 3-5 



1800 



4 2-5 



4 1-8 



3 30-1 



3 300 



1900 



4 320 



4 31-4 



3 595 



3 59-4 



2000 



5 35 



5 35 



4 31-8 



4 31-9 



2100 



5 370 



5 38-2 



5 7-2 



5 7-8 



2200 



6 125 



6 15-7 



5 45-9 



5 47-5 



2300 



6 50-0 



6 56-4 



6 28-2 



6 31-5 



32. Motion of the Axis of the Shot. — Reasoning from the 

 behaviour of a spinning-top, we should expect that a pro- 

 jectile with sufficient spin would keep its nose forward 

 throughout the motion. But in the case of the top the 

 force acting on it, namely, gravity, acts in a fixed direction, 

 whereas the resistance to a projectile rotates with the line of 

 flight. The precise behaviour of the axis of the shot cannot, 

 therefore, be foreseen from that of the top. In the follow- 

 ing investigation it is shown that the axis pursues the line 

 of flight while lagging a little behind it, the angle of lag- 

 increasing with the range. Moreover, the axis of a shot 

 having right-handed spin is deflected a little to the right 

 (and for left-handed spin, to the left) of the line of flight. 

 The action of the air on the side of the shot exposed by 

 the deflexion of the axis causes a shot with right-handed spin 



