BUOYANCY OF WATER 149 



From this experiment we learn that a body submerged in 

 water displaces a volume of water equal to its own volume. 

 A cubic block measuring exactly 96 cubic centimeters 

 would displace 96 cubic centimeters of water. 



Experiment 69. Attach the block prepared for the previous 

 experiment to a spring balance with a scale reading in grams, and 

 weigh it. Lower the block suspended from the scale by a thread 

 into a vessel of water until it is entirely submerged. Does the 

 block appear to weigh as much now as when out of water ? 



Compare the difference between the weight of the block in air 

 and its apparent weight in water, with the weight of the water 

 which the block displaced in the preceding experiment. One cubic 

 centimeter of water weighs a gram. 



From this experiment we learn that a body appears to 

 lose weight when it is submerged in water and the amount 

 of weight it loses is exactly equal to the weight of the vol- 

 ume of water it displaces. If a cubic centimeter of lead is 

 weighed in water it will be found to weigh one gram less than 

 in air. In other words the lead is pushed upward, or buoyed 

 up, by a force exactly equal to the weight 

 of a like volume of water. 



Experiment 70. If convenient use an " over- 

 flow can." If not punch a hole near the top of 

 a, IflVrfffi tin nan. CDrivft thft nnnp.h frrvm the 



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a large tin can. (Drive the punch from the 

 inside so that the flange will be on the out- 

 side.) Smear a little vaseline around the inside 

 and the outside of the hole so that water will 

 not cling to the tin. Place the can on a box on FIGURE 77 

 the table and fill with water until the water 

 begins to run out of the hole. (Figure 77.) Accurately weigh a 

 block similar to the block used in Experiment 68, but containing 

 no lead. Weigh also a dry beaker. Place the beaker so that it 

 will catch all the water overflowing from the hole in the tin can. 

 Place the block in the can. As soon as water has ceased to run 



