EXERCISE 3 

 DOES AIR HAVE WEIGHT? 



Materials. A football ; a bicycle pump ; a pair of balances. 



Directions. Pump into the football all the air which can be forced into it without danger of burst- 

 ing it. Weigh the football accurately and record the weight. Open the tube of the football and allow 

 as much air to escape as can be done without allowing the football to collapse. Weigh accurately 

 again. Compare and explain any difference between the two weights. 



Additional problem. Do you think that a given volume of liquid air would weigh more or less than the 

 same volume of ordinary air ? Why ? 



[3] 



