FLUID PRESSURE 



33. Cause of Pressure in Liquids. If a liquid flow 

 or be poured downward until it is stopped, gravity 



still acts upon it and 

 causes it to push upon 

 whatever stops it. 

 Thus when the flow of 

 a liquid is stopped by the 

 bottom and sides of a dish, a 

 pond, or even the ocean, the 

 liquid exerts force upon those 

 sides and the bottom. Each 

 particle is still acted upon 

 by gravity, and in an effort 

 to go lower it exerts force 

 upon the particles around it 

 in all directions. For this 

 reason water will spurt from 

 a leaky hose equally in any 



direction. This principle may be stated as follows : At 

 the same depth in a liquid, pressure is 

 equal in all directions. 



Experiment 21. Cover the end of a lamp 

 chimney with cardboard and push it into water 

 in a glass dish (Fig. 9). Pour water into the 

 chimney till it reaches the same level as the 

 water outside. Add a bit more water and watch 

 the result. Explain what you see. 



Experiment 22. Bend three tubes, as a, b, 

 and c (Fig. 10), so that the ends may open 

 upward, downward, and sidewise. Put equal 

 quantities of mercury into each, so that it may 

 stand at the same level in all. Now lower the tubes into water till 



FIG. 10 



