LAWS OF MATTER 453 



3. One leans forward in getting up from a chair. Why? 



4. It is difficult to balance a ruler on one end on the finger. Why? 



5. When one is standing in a swaying street car he is more secure 

 with his feet farther apart than usual. Why? 



6. A tall, slender vase is more likely to tip over than a short, 

 thick one. Why? 



7. Why are some inkwells made cone-shaped with thick bot- 

 toms? 



8. A canoe overturns more easily when a person stands up in 

 it than when the person is sitting down. Why? 



9. Why is a wagon loaded with hay more likely to tip over 

 on a hilly road than one loaded with rocks? 



10. " Ballast " is placed along the keels of sailing vessels to 

 prevent capsizing. Why? 



11. The engines of motor boats are set as low as possible in the 

 boat. Why? 



12. Why are some oil cans and inkwells made with round bottoms 

 and loaded with lead at the bottom? 



13. As one climbs a steep ladder he has to be more careful as he 

 climbs higher. Why? 



14. It is easier to balance a china bowl on the end of the finger 

 when the bowl is upside down than when it is upright. Why? 



15. Why is a tail placed on a kite to prevent it from " diving "? 



16. Why is a tricycle less likely to upset than a bicycle? 



17. If one stands with his heels against the wall and tries to pick 

 up a coin placed between his feet he cannot do so without falling. 

 Why? 



18. Why are tall vases sometimes prevented from tipping over 

 by placing sand in them? 



19. What is friction? 



20. Why can we not push a nail into wood? 



21. Why must water be kept continually on a grindstone when 

 grinding knives? 



22. Why does a hone sharpen a razor? 



23. Why do skates make grooves in the ice? 



