CHAPTER XL 

 LAW OF FLOATING BODIES. 



24. FLUID DISPLACEMENT AND FLOATING BODIES. 



i. Some things sink others float in water. Fill a pneumatic trough with 

 water, and carefully place lumps of different things, e.g. pieces of lead, iron, 

 oak, pine and cork, one after 

 another, into the water. Ob- 

 serve that (1) some sink and 

 others float, (2) of those which 

 float some sink further into the 

 water than others. Take the 

 objects which sink in water and 

 place them in mercury. Notice 

 that they float. (Fig. 42). 



ii. Volume of water displaced 



by solids which float. (a) Obtain 



a rectangular rod of wood, 1 



square cm. in section and about FIG. 42. When substances are denser than 



15 cm. long, with lines around it f w h ater fl th f ey sh)k in water; and if less dense ' 



1 cm. apart. Gouge a small 



piece of the wood out of one end, and put lead into the hole ; flatten the 



end by filling in with wax. 



Put some water in the graduated jar and notice its level. Find the 

 weight of the rectangular rod, and then place 

 it in the jar with the leaded end downwards. 

 Notice how many cubic centimetres of the 

 rod are immersed, and also how many cubic 

 centimetres of water are displaced (Fig. 43). 

 Since the weight of 1 cub. cm. of water is 1 

 gram, the number of cubic centimetres of 

 water displaced is also the weight in grams 

 of the water displaced. This weight will be 

 found equal to the weight of the whole rod. 



(6) Weigh one of the larger wooden cubes. 

 Slightly oil the cube and place it in a beaker 

 of water. Mark upon the cube with a pencil 

 where the surface of the water touches it. 

 Then take out the cube and determine the 

 volume of the immersed portion in cubic 

 55 



FIG. 43. The number of cubic 

 centimetres in the part of the rod 

 under water is equal to the num- 

 ber of cubic centimetres of the 

 water displaced. 



