392 OUTEOOR RECREATION 



Experiment. To demonstrate gyroscopic motions. 



Materials: A toy gyroscope. 



Method and Results: Set the wheel in motion. How long will it spin 

 with vertical axis? Set in motion and rest one end of axis on the 

 wooden support, with a horizontal axis. If the wheel were not spinning 

 would it stay in that position? Set in motion again. Take hold of 

 one end of axis and quickly change from vertical to horizontal. Com- 

 pare the resistance to this movement when the wheel is revolving to 

 that when the wheel is still. 



Conclusion: What are some laws of gyroscopic action suggested by these 

 experiments? How can the gyroscope act as a stabilizer of ships and 

 airplanes ? 



Darts, slings, and bows and arrows. Any toy that 

 can be made is of more interest than one we buy, and 

 toys which allow us to play in competition with others 

 so that our skill is matched against that of the other 

 fellow, are most interesting of all. Long years ago 

 dwellers on the earth used the sling, the dart, and bow 

 and arrow as a means of getting their food as well as 

 weapons for offense and defense. We all know the story 

 of David and Goliath, and who has not read of the early 

 days in this country when Indians not only shot their food, 

 but also killed their enemies with a bow and arrow ? Very 

 briefly some of the science underlying their use may be 

 mentioned here. For example, in the dart, or in the arrow, 

 why do we have pointed tip, and feathers or pieces of stiff 

 paper at the hind end of the dart or arrow ? The elasticity 

 of wood, metal, and cord is also strongly shown in the case 

 of the bow. In the use of the sling, when we whirl the sling 

 round and round before releasing the missile, we have a good 

 example of centrifugal force. This is the force which would 

 cause each one of us to fly off the surface of the earth as it 

 goes whirling around in space were it not for an opposing 

 force which holds us down, the force we call gravity. 



