308 



TRANSPORTA TION 



TOPIC 3. TRAVEL IN THE AIR 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What is the history of the balloon? 



2. What are the various types of dirigible bal- 

 loons, and what principles control them? 



3. What is the history of heavier-than-air de- 

 vices? 



4. Why does the airplane stay up? 



5. How is the airplane controlled? 



6. What are some of the achievements of the 

 airplane and the dirigible? 



7. What are some of the recent developments in 

 aviation? 



8. Of what importance are the dirigible and the 

 airplane in modern transportation? 



SUGGESTIONS AND HELPS FOR STUDY 



1. Great developments are taking place in the field 

 of aviation. In this topic you will have an opportunity 

 to learn about the basic principles of air transporta- 

 tion. 



2. Many newspapers and magazines contain in- 

 formation about dirigibles and airplanes. Sometimes 

 they give directions for building small model planes. 

 Have you ever tried to build a model of an airplane? 

 Try it. 



3. The following words may be new to you. 



hydroplane an airplane built to land on water. 



rudders devices used to guide an airplane. 



ailerons movable pieces attached to the outer ends of 



the wings of an airplane. 

 helium one of the lightest known gases, which is now 



being used in dirigibles in this country. 

 helicopter an airplane which can rise straight from the 



ground or be landed in a small space. This is made 



possible by a large revolving propeller placed on top 



of the plane. See Figure 525. 



EXPERIMENTS OR DEMONSTRATIONS WHICH WILL 

 HELP ANSWER THE PROBLEM QUESTIONS' 



Experiment 181. Why does a balloon rise? 



Make a thick soap solution by dissolving soap in warm 

 water. Attach a short length of glass tube to a gas jet 

 or a hydrogen generator by means of a rubber tube. Blow 

 bubbles with the gas and detach them from the tube by a 

 slight jerk. Observe what happens. 



Fill a rubber balloon with hydrogen gas. This may be ac- 

 complished by first filling a large bottle with the gas and 

 then using water pressure to force the gas into the balloon. 

 See Figure 514. Fill another balloon with carbon dioxide. 

 What happens in each case ? 



Record your observations and answer the following ques- 

 tions. 



1 See workbook, p. 112. 



Why does the balloon filled with hydrogen behave as it 

 does ? Why does the balloon filled with carbon dioxide behave 

 as it does? What gases are used in dirigibles? 



Activity 182. What notable flights have been made? 



Prepare a list of great flights that have been made in 

 airplanes and dirigibles. Give the names of the fliers, date 

 of the flight, type of machine, and a brief description of the 

 flight. Collect pictures of the fliers and the machines in 

 which these flights were made. 



READINGS WHICH WILL 



HELP ANSWER THE 

 PROBLEM QUESTIONS 



What is the history of 

 the balloon? In this age of 

 aircraft it seems strange 

 that the ancient Greeks 

 were among the first to 

 think of the use of air for 

 transportation. Records 

 show that Archytos, a 

 Greek scholar of the 

 fourth century before 

 Christ, constructed a 

 wooden bird for the pur- 

 pose of flight. It is interesting to note that from the 

 dreamings and crude experiments of these early 

 Greek philosophers no practical results came until the 

 eighteenth century, when the balloon was invented. 



The invention of the balloon is commonly credited 

 to the Montgolfier brothers, Frenchmen. In 1783 they 

 inflated and raised the first balloon. Before this, how- 

 ever, Cavendish, an Englishman, had discovered hy- 

 drogen, the lightest of the elements, and had predicted 

 that light bags filled with this gas were sure to rise. 

 Before resorting to the gas from burning straw and 

 wood to 'fill their silk balloons, the Montgolfiers had 

 experimented with hydrogen in paper bags. After 

 these experiments they made a larger balloon and 



FIG. 514 



Courtesy Goodyear Tire and Rubber Company 



FIG. 515. NON-RIGID DIRIGIBLE 



