352 Introduction to the Study of Science 



sure to the volume of water? 9. What would happen to a flat-sided 

 bottle which is stoppered and sunk in the deep sea ? 10. What facts 

 should builders of boats know? 



11. What is the meaning of density? Of relative density? 

 12. Will iron float or sink in melted zinc ? In melted lead ? 13. How 

 much of a cork is under water? Of a block of pine? Of a block of 

 oak ? 14. Compare the volumes of a pound of cork and a pound of pine. 



15. What is the importance of stability in boats? 16. Describe 

 how the center of weight of a piece of board may be found. 17. What 

 is meant by the center of buoyancy? 18. What are the relative 

 positions of center of weight and center of buoyancy when a boat 

 tends to right itself? When it tends to overturn? 19. In designing 

 a boat what is planned to give great stability ? What can be done in 

 loading the boat? 20. How is the idea of stability applied to other 

 things than boats? 



21. Mention some simple means of propelling boats. 22. Com- 

 pare the oar with the paddle. 23. Show that the oar is a form of 

 lever. 24. Give an illustrative problem to show the forces that come 

 into play when the oar is used. 25. Explain why the backward push 

 of the blade against the water drives the boat forward. 26. State the 

 law of reaction. 



SUGGESTIVE QUESTIONS 



1. What do you imagine would be the result of trying to swim in a 

 tank of mercury? (Density = 13.6.) 2. What if one should fall 

 into a tank of gasoline? (Density 0.7.) 3. Boats before launching 

 are often painted one color above the water line and another below. 

 What must be known to determine the position of the water line? 

 4. Some governments require that a licensed ship have marked on its 

 side the water line as it would be when the ship is loaded with the total 

 weight of cargo allowed for safety. How does the government in- 

 spector know where the line should be? 5. In rivers near the ocean 

 fresh water may be on top and salt water below. Explain. 



6. What sort of stability has (a) a boat ? (6) a table ? (c) an orange ? 

 (d) a football player? (e) a tree trunk? (/) a cube? (g) a -dog? 

 7. Why does a person lean forward when carrying a heavy load on ' 

 back or shoulders? To one side when carrying a suitcase with one 

 hand? 8. Can you stand with both heels against a wall and pick up 

 a hat in front of you without falling? Why? 9. Why is a racing 

 automobile made to run close to the ground? 10. Why do racing 

 yachts have a very deep keel? 11. Why will a boat tip more easily 

 when its occupant is standing than when sitting down? 12. When 



