86 MOVEMENT 



Ballistic Experiments. — Chronophotography can re- 

 cord the path taken by projectiles which travel slowly, 

 and can show that the behaviour of such bodies is in 



r'lG. 55. — The successive positions of a projectile in respect to two axes, one vertical, 

 the other horizontal. 



accordance with the shape and the character of the 

 propelling force. When a round projectile is thrown 

 in a horizontal direction, the course taken is obviously 

 parabolic ; it is, however, affected by the resistance of 

 the air, as will soon be shown. If the projectile de- 



Fig. 56.— Stick thrown horizontally with a rotatory movement in a vertical plane. 



parts from the circular form ; if, for instance, it is a 

 stick which is thrown in a vertical plane with a rota- 

 tory motion, the images of the stick will be found to 

 lie in all directions, but the centre of gravity, i.e. the 

 middle of the stick, will follow a parabolic course (Fig. 

 56). 



