IN NATURAL PHILOSOPHY. 29 



36. A vessel holds 10 Ibs. of water: how much n.trcury 

 would it contain ? 



Mercury is 13.5 times heavier than water. Hence the vessel would contain 

 10 Ibs. x 13.5 = 135 Ibs. of mercury. 



37. A stone weighs 70 Ibs. in air and 50 in water. What 

 is its bulk ? 



70 50 = 20. 20 x 15 oz. = 320 oz., the weight of water displaced. 

 320 oz. is % of a cu. ft. 



38. A hollow ball of iron weighs 10 Ibs. : what must be its 

 bulk, to float in water? 



10 Ibs. = 160 oz. As a cubic ft. of water weighs 1,000 oz., the ball must dis- 

 place such a part of a ca. ft. of water as 1,000 oz. is contained times in 160 oz 

 which is .16 en. ft. 



HYDRAULICS. 



521. i. How much more water can be drawn from a faucet 

 , than from one 4 feet below the surface of the water in a 

 cistern ? 



y = 2 Vffd ; hence v = 2 V 7 16 x 8 = 2S.6. 

 v = 2 N/16x4 = 16. 



Hence 6.6 cu. ft. more would flow from one than from the 

 other in each second. 



2. How much water would be discharged per second from 

 a short pipe having a diameter of 4 inches and a depth of 48 

 feet below the surface of the water ? 



4 2 =16. IP. x .7854=12.57 sq. inches=.087 sq. ft. (area of the tube). 



v = &Sgd = 2^16^48 = 55.4 



.087 x 55.4 = 4.8 cu. ft. 



3. When we pour molasses frojn a jug, why is the stream so 

 much larger near the nozzle than at some distance from it? 



Because, according to the law of falling bodies, the further 

 the molasses falls the faster it falls. The stream, therefore, 

 becomes smaller as it moves more swiftly, until, at last, it 

 breaks up into drops. 



