Transportation Water and Air 289 



20. If an airplane motor were powerful enough, would there be any limit 

 to the distance it could rise above the earth? 



21. Name all the present uses of airplanes you can think of. 



22. Why do toy balloons sometimes burst when they reach considerable 

 heights ? 



23. Why is a balloon likely to descend somewhat at nightfall? 



24. What is the difference between seaplanes and other airplanes? 



25. Is it more difficult to sustain an airplane at an altitude of one mile 

 than at an altitude of four miles? Why? 



26. What is a parachute? How does it work? 



PROJECTS 



1. Construct a balloon and fill it with heated air. Let it rise and record 

 your observations of its movements. 



2. Construct a kite. Fly it. Experiment with different cord connections 

 to bring it at different angles to the wind. Record your findings. 



3. By reference to some standard book, construct an airplane model. 

 Test it out in the air and record your observations. Make a labeled 

 drawing of it. 



4. Construct a model sailboat by reference to some standard book. Sail 

 it on a pool or small body of water and observe the effect of the wind 

 upon it under different conditions. Record your observations. 



OUTDOOR OBSERVATION 



1. Examine, if possible, a sailboat and a steamship. Study their main 

 parts and observe them when in motion. 



2. Watch a kite and an airplane in flight and record your observations. 



REFERENCES 



The Boy's Book on Model Airplanes , Collins 



The Romance of Air Craft. . Smith 



