EXERCISE 20 



IS AIR COMPRESSIBLE? 



Materials. Glass tubing -1 inch in diameter ; a small glass funnel ; rubber tubing to 

 tubing ; pinch clamp ; small wire ; mercury. 



Directions. Bend a 5-foot length of glass tubing to make a U-shaped tube with the 

 arms about 4 inches apart. Wire this to a board or clamp it firmly to a ring stand in an 

 upright position. To one end of the tube attach a small funnel by means of a rubber 

 connection. Slowly pour in enough mercury to make a column about 2 inches high in 

 each arm of the tube. To the other end of the tube attach a rubber connecter closed 

 with a pinch clamp. Measure the length of the air column in the closed arm of the tube. 

 Now add mercury through the funnel and note the effect upon the volume of the air in 

 the closed arm. Has any of the air escaped ? How has it changed ? When the open arm 

 is nearly filled with mercury, slowly open the pinch clamp and listen for any evidence 

 which will help you to answer the above questions. 



Additional problems. When an automobile or bicycle tire is said to be full of air can more 

 air be pumped into it ? 



What causes the loud report when an automobile tire bursts ? 



In a flask which is one fourth filled with water, insert a rubber stopper through which 

 a glass tube extends almost to the bottom of the flask. The outer end of the tube should be 

 drawn to a fine opening. Blow through the tube; note and explain what occurs when you 

 stop blowing. 



fit the glass 



A 



! =<K 



[25] 



