84 APPLIED SCIENCE 



4. How can the pressure of ji liquid on the surface be ascer- 

 tained? 



5. Will the perpendicular sides of a trough tilled with liquid 

 sustain the same pressure, whether the trough be narrow or wide? 



6. Explain the principle of science underlying hydraulic 

 machines. 



7. Name some of the applications of hydraulic machines. 



8. Why does deep sea diving often cause pain and bleeding 

 in the ears and nose? 



9. Explain the importance of a knowledge of the principle of 

 -specific gravity in the trades. 



10. Explain how a modern warship floats although made entirely 

 of steel, its walls being of steel plate from 6 to 18 in. thick. 



11. What is the water-line of a boat? 



12. A boat passes from fresh into salt water. Will the water- 

 line rise or fall? 



Problems 



1. What is the weight of a rectangular block of hardwood 

 with the dimensions 8 ft. 4 in. X 7 ft. 6 in. X 3 ft. 3 in.? The 

 specific gravity of wood is .7. The weight of a cubic foot of water 

 is 62.5 Ibs. 



2. What is the weight of a cylindrical block of soft seasoned 

 wood 8 in. in diameter and 4 ft. long? The specific gravity is .5. 

 The weight of a cubic foot of water is 62.5 Ibs. 



3. What is the weight of salt water in a rectangular tank 

 5 ft. 2 in. X 4 ft. 7 in. X 3 ft. 5 in.? The specific gravity of salt 

 water is 1.03 and the weight of a cubic foot of water is 62.5 Ibs. 



4. Express in pounds per square inch a "bend of 69 ft." 



5. What is the pressure near the keel of a vessel drawing 18 ft. 

 of water. (Salt water has specific gravity 1.03.) 



6. A hole is cut in the bottom of a ship drawing 17 ft. of water. 

 What force is necessary to hold a plank tightly against the hole? 



7. It is desired to have a pressure of 60 Ibs. at a hydrant. 

 How high must the reservoir be above the main? 



8. A rowboat weighs 230 Ibs. How many cubic feet of water 

 does it displace? A cubic foot of water weighs 62.5 Ibs. 



