FLUID PRESSURE 



particles exert, it follows that the force tending to hold 

 it up is equal to the weight of the displaced liquid. In 

 other words, any body held in a liquid is buoyed up by 

 a force equal to the weight of the liquid displaced. 



Experiment 25. Fill a vessel a (Fig. 13) with water, so that 

 no more can be added. Weigh some heavy body in air and again 

 while dipped in the water, as in Fig. 13. Note the loss of weight. 



a b 



FIG. 13 



Arrange a vessel b so as to catch the water which spills from a 

 as r is lowered into it. Weigh the water caught, comparing with 

 the loss of weight just found. 



39. Floating Bodies. The specific gravity (see 31) 

 of many substances is less than that of water; such 

 bodies float upon its surface. If any body floats upon a 

 liquid surface, neither rising nor falling, it is clear that 

 its weight is just balanced by the buoyant force acting 

 upon it. But we have learned that buoyant force is 

 always equal to the weight of liquid displaced. From 

 these two facts we can easily form the Law of Floating 

 Bodies : Floating bodies displace an amount of liquid 

 equal to their own weight. 



