EXERCISE 5 



SINCE AIR HAS WEIGHT, DOES IT PRESS DOWNWARD AS OTHER 



HEAVY OBJECTS DO? 



Materials. A piece of sheet rubber (dentist's rubber) about 6 or 8 inches square ; a bladder glass 

 ("Elements of General Science," Fig. 5); an air pump (or a filter pump as described in Exercise 3 A, 

 together with a pump platform). 



Directions. Tie a piece of thin sheet rubber across the top of a bladder glass. When the rubber is 

 first placed upon the glass, no pressure of the air upon the rubber is noted, because there is air both 

 below and above the rubber. In order to know whether there is pressure upon the rubber, we may 

 remove the air from beneath. To do this, place the glass upon the platform of an air pump and 

 remove some of the air. 



What are the results and your conclusions ? 



Additional problems. Why are we not conscious of the pressure of the air upon us ? 

 With a hand placed over the bladder glass remove some of the air from the glass. Why is suction not 

 a good name for the results observed when the air is partly removed from beneath the hand ? 



[6] 



