CHAPTER VII 



PRINCIPLE OF ARCHIMEDES, AND RELATIVE DENSITY 



Principle of Archimedes. Every one has noticed, when in 

 water, that the body is buoyed up and appears lighter than when 

 on land. The liquid appears to exert an upward force of buoyancy 

 which partly counteracts the 

 weight of the body. The force 

 which a liquid exerts upon an 

 object immersed in it is measured 

 in the following experiments : 



EXPT. 77. Suspend from a 

 spring balance a metal ball or 

 cube or cylinder, the volume 

 of which is known or can be 

 calculated from the dimen- 

 sions. Or, instead, use any 

 object, such as a glass stopper, 

 the volume of which has pre- 

 viously been determined by 



displacement of water (see Expt. 43). Notice the weight 

 of the object in air, when suspended from the balance ; then 

 immerse the ball in a glass of water and observe the apparent 

 loss of weight (Fig. 40). 



FIG. 40. Loss of Weight in Water. 



