CHAPTER VII 

 MECHANICS OF LIQUIDS 



67. The Utilization of Liquids in Industry. Liquids, 

 particularly water, possess certain properties which render 

 them invaluable for many industrial purposes. These 

 properties form the bases upon which hydraulic machines 

 and many other devices are constructed. To know how to 

 use all these contrivances efficiently and intelligently, it is 

 necessary to know the principles underlying them. 



68. General Properties of Liquids. Water and all other 

 liquids resemble solids in that they possess a definite size; 

 that is, they occupy a definite space. Liquids differ in that 

 they have no definite shape. The shape of a liquid is the 

 shape of the vessel which holds it. A solid has a definite 

 shape and retains it until acted upon by a force greater 

 than the cohesive strength of its particles. The force of 

 gravity is continually forcing liquids to seek the lowest leveL 

 This fact is illustrated when two vessels containing the same 

 liquid are connected. The level in each becomes the same, 

 regardless of the form or distance of the connecting pipe. 

 This peculiarity of liquids is commonly expressed by the 

 saying "water seeks its own level." 



A force of any kind, however small, will change the shape 

 of a liquid. To illustrate : If a pebble is dropped into a pond 

 it moves the whole of the water and the motion can be seen 

 by the ripples which form on the surface of the pond. The 



68 



