1 1 



1 1 YM; \ rues AND ITS APPLICATIONS 



motions and forces involved are of such complexity as to prevent any 

 attempt at a solution from d ]>ri<>ri reasoning based solely on a knowledge 

 of the physical properties of the fluid. 



Although from the definition of viscosity, the stresses in different fluids 

 under similar circumstances of motion will be proportional to their values 

 of //, yet in com pa ring the effects of viscosity in modifying such motions 

 it is the ratio of these stresses to the inertia of the fluid which must be 

 taken into account. Thus the determining factor is n -f- p. (Cf. p. 71.) 

 From this point of view air is a much more viscous fluid than water, as 

 will be seen from the following figures. 



From these it appears that at 60 F. the relative effect of viscosity in 

 modifying the motion is practically thirteen times as great in the case of 

 air as in the case of water. 



The energy absorbed in overcoming viscous resistance in any fluid 

 motion finally appears in the form of heat which is dissipated by 

 conduction and radiation. 



