a Sphere in a Viscous Fluid, 527 



motion through the liquid. This will include at least two 

 terms, one arising from the motion in a viscous fluid with 

 velocity V, and the other involving the acceleration of the 

 sphere. As we have no means of separating the effects, we 

 cannot in this way deduce the resistance experienced by a 

 sphere moving with constant velocity through a viscous 

 fluid. 



The following values of E, were calculated from the curve: — 



Table VI. 



S, cm. 



V, cm./sec. 



/, cm./sec. 2 



R. 





3 



54-0 



415 



566 

 981 W - 



441 

 981 W ' 



5 



65-2 



294 



981 



562 

 981 W - 



7 



72-2 



227 



754 W . 



981 



981 w - 



9 



77-5 



151 



830 w 

 981 



705 W 

 981 ' 



11 



80-2 



75 



906 w 

 981 



781 w 

 981 



Terminal. 



83-0 







W. 



856 w 

 981 ' 



The rate at which the acceleration falls off increases 

 suddenly when the velocity is about 75 cm./sec. This would 

 seem to show that the law of resistance to the steady motion 

 of the sphere employed undergoes a sudden change for this 

 particular velocity. 



10. Terminal Velocities of Steel Balls. 



In the case of the two smallest balls, the depth of the glass 

 vessel was great enough to allow of the terminal velocity 

 being attained. But for the larger balls it was found 

 necessary to increase the possible height of fall. This was 

 done by allowing the ball to fall through a vertical glass 

 tube filled with water and having its open end beneath the 

 surface of the water in the vessel. In order to suspend the 

 ball from the electromagnet hermetically fitted into the top 

 of the tube, and then fill the latter with water, a circular 

 opening was made in the side of the tube close to the top. 

 Through this opening the ball was introduced. Then the 

 aperture was closed by a rubber bung, through which passed 

 a short tubulure for the purpose of filling the tube by suction 



