66 APPLIED SCIENCE 



lated. The same accumulation of energy takes place in run- 

 ning before taking a jump. This accumulated energy or 

 method of gathering momentum is utilized in machines by 

 placing a fly-wheel on the driving shaft. When such a wheel 

 revolves, the momentum will cause it to run a long time after 

 the power has been shut off, due to the energy stored in the 

 fly-wheel. 



Questions 



1. Explain why the wind is able to do the work of turning a 

 windmill. 



2. When the wood-chopper chops wood he usually swings the 

 axe high when he comes to a knotty piece. Why? 



3. Why is it more comfortable to ride in a carriage with pneu- 

 matic tires and springs than in a farm wagon with neither? 



4. Explain why fortifications are usually made of earthwork 

 and not masonry. 



5. When an automobile runs too fast around a corner it " skids." 

 Why? 



6. Explain why a person riding in a rapidly moving railway 

 car is thrown forward when the car stops suddenly. 



7. Explain why a person standing in a street car is thrown 

 back when the car starts suddenly. 



8. (a) In attempting to kick the panel out of a door why does 

 one experience a pain from the kick? (b) This pain is not severe 

 when you kick a canvas curtain. Why? 



9. Why does a man lean forward when he climbs a hill? 



10. (a) What is the ballast of a ship? (b) What is the object 

 of the ballast? 



11. Why is it unsafe to stand in a canoe? 



12. Which is more steady (stable) a load of wood or a toad of 

 metal equal in volume? 



13. Explain the principle of a revolving clothes-dryer used in 

 laundries. 



14. The outer rail of a railroad curve is higher than the inner 

 one. Why? 



