12 



THE OCEAN OF AIR 



than a lift pump because of the 

 dome. 



developed in the air 



10. The siphon operates because of unequal 

 bv-unequal lengths of the 



caused 



of the following devices in some way make 

 use of a vacuum or partial vacuum? 



Automobile gasoline line, air brake, sink opener, can opener, 

 lift pump, electric light bulb, rubber heels, automobile cylin- 





FIG. 25 



der, automobile windshield wiper, electric flatiron, some 

 types of washing machines 



12. Which two of the words or phrases after the dash are 

 most closely associated with the key word before it? 



a. vacuum vacuole, varicose, reduced pressure, increased 

 pressure, lift pump 



b. siphon lower level, air pressure, vacuum, valve, ver- 

 tical 



13. Air enters the lungs because the is decreased 



by of the 



14. Figure 25 is the diagram of a double acting force 

 pump; from your knowledge of force pumps explain how 

 this one operates and state its advantages over the common 

 force pump. 



15. A farmer, after driving a well, attached a lift pump 

 to the pipe and found that it would not pump the water 

 which he was sure he had struck. In driving the well he 

 had used six-foot lengths of pipe. Cite the possible causes 

 of the failure of the pump to work and show how you would 

 proceed to locate the actual cause. 



16. Dirt and dust are pushed into the nozzle of a vacuum 

 cleaner. Choose from the following group of statements 

 those which would be important in establishing the truth 

 of the statement above. 



(a) The vacuum sweeper will not pick up heavy ob- 

 jects. 



(b) Air blows through the fine meshes of the bag. 



(c) The sweeper works better on rugs than on floors. 



(d) It is difficult to pick up bits of paper with a vacuum 

 sweeper. 



(e) The bag of the sweeper bulges out when the motor 

 is running. 



(f) The motor turns a fan. 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What are some of the modern devices that use 

 compressed air? 



TOPIC 3. JttAN'S USE OF COMPRESSED AIR 



gauge a device for measuring steam, gas, or water 

 pressure. 



piston a sliding cylinder fitting inside another cyl- 

 inder along whichji-moves ; used in steam, gas, and 

 oil engii 



2. How does compressed air enable men to work 

 under water? 



SUGGESTIONS AND HELPS FOR STUDY 



1. Carefully study the problems suggested above 

 until you are thoroughly familiar with them ; then be- 

 gin their solution by doing the experiments and read- 

 ings suggested below. FqUow the same plan used in 

 the two previous tep"Tcs7 Refer to it and review it 

 carefully before beginning. 



If the problems of this topic appeal to you, you will 

 find fascinating reading in the special references that 

 are listed on pages 26 and 27. 



2. Master the meaning of the following new words 

 which you may find in this study : 



caisson a large hollow cylinder made of steel and 

 open at the bottom, used to enable men to work 

 at the bottom of a river or other body of water. 



EXPERIMENTS OR DEMONSTRATIONS WHICH WILL 

 HELP ANSWER THE PROBLEM QUESTIONS 



Experiment 9. How can a model caisson be made? 



Place a glass funnel in a pan of 

 water as illustrated in Figure 26. 

 Attach a short length of rubber 

 tube to the stem of the funnel and 

 increase the air pressure on the in- 

 side by blowing through the tube. 

 Float a cork or small piece of wood 

 under the funnel and repeat the ex- 

 periment. When the pressure has 

 been increased, close the tube with 

 a clamp or a string. 



In your notebook 1 record the 

 notes of this experiment and com- 

 plete the following statements. 



1 See accompanying workbook, p. 7. 



FIG. 26 



