DYNAMICS OF CYCLONES AND ANTICYCLONES. 



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complications due to the effects of gravity owing to the balls falling a short distance 



as they approach the centre, suspend the balls from the opposite ends of a short beam 



B, suspended by fine wires, C C, as shown in the figure. The upper ends of the wires are 



fixed to a swivel D, to enable the balls to be put into circular 



movement round their common centre. To each of the balls a 



short cord EE is attached. These cords are passed through a 



small ring F, which is suspended at the level of the balls by the 



wire G fixed to the swivel D. The two cords EE are joined 



below to another swivel H, which has a cord attached to its lower 



end, to allow the balls to rotate round G, whilst the lower cord is 



held in the hand. If we now put the balls into a slow circular 



movement round their common centre, and take hold of the lower 



central cord below the swivel H, note the rate of revolution and 



pull the cord downwards. This will draw the balls towards the 



centre of motion, in the same way as the particles of water are 



drawn into the centre of the vortex. When this is done it will be 



seen that the initial slow motion is rapidly quickened, and that 



when the balls are near the centre they are whirling round each 



other at a great velocity. 



Another way of making this experiment is to remove the 

 small ring F and its suspending wire, and tie the balls with a cord 

 of about 50 cm. long, then attach to this cord, at a point halfway 

 between the balls, a small rod held vertically. If the balls be 

 now made to rotate round the rod, and the rod be prevented from 

 turning, the balls will gradually wind themselves towards the 

 centre, and it will be noticed when making the experiment in this 

 way that whilst the angular velocity increases, the absolute 

 velocity does not, showing that the mere fact of the balls 

 approaching the centre has nothing to do with the increase in the 



velocity observed in the previous experiment. If now, in place of holding the centre 

 rod firm, we cause it to rotate on its vertical axis so as to wind the balls towards the 

 centre, it will now be seen that the absolute as well as the angular velocity is greatly 

 increased, as was seen in the previous experiment, in which the balls were drawn 

 together by means of the cords E E. The balls now fly round so quickly the eye can 

 hardly follow them. 



Further, it will be noticed that the balls offer a rapidly-increasing resistance to the 

 centripetal force. This to a certain extent is to be expected, because as the balls 

 approach the centre the centrifugal force increases ; if the velocity is constant it is 

 double what it was at first by the time the balls are drawn half way to the centre. 

 But on account of the increased velocity which we cannot avoid giving the balls in the 

 process, they are enabled to offer still greater resistance to the centripetal force. This, 



Fig. 1. 



