EXAMPLES. 83 



20. A sovereign, whose weight is 123.02 grs., weighs in 

 water 116.02 grs. Required its specific gravity. 



Ans. 17.574. 



21. Find the specific gravity of a piece of wood whose 

 weight is 50 grs. To sink it we attach a brass weight 

 which, when immersed in the water, weighs 87.22 grs. ; the 

 weight of the compound body when immersed is 42.88. 



Ans. 0.53. 



22. A piece of wood weighs 4 Ibs. in air and a piece of 

 lead weighs 4 Ibs. in water ; the lead and wood together 

 weigh 3 Ibs. in water. "Find the specific gravity of the 

 wood. Ans. 0.8. 



23. A body immersed in water is balanced by a weight 

 P, to which it is attached by a string passing over a fixed 

 pulley ; when half immersed, it is balanced in the same way 

 by a weight 2P. Find the specific gravity of the body. 



Ans. f. 



24. Find the weight of a cubical block of stone whose 

 side is 4 ft, and specific gravity !. Ans. 80000 oz. 



25. A body weighing 20 grs. has a specific gravity of 2. 

 Required its weight in water. Ans. 12 grs. 



26. An island of ice rises 30 ft. out of the water, and its 

 upper surface contains f of an acre. Supposing the mass to 

 be cylindrical, required (1) its weight, and (2) depth below 

 the water, the specific gravity of sea-water being 1.0263, and 

 that of ice .92. Ans. (1) 242900 tons; (2) 259.64 ft 



27. A piece of wood weighs 12 Ibs., and when attached 

 to 22 Ibs. of lead and immersed in water, the whole weighs 

 8 Ibs. The specific gravity of lead being 11, required that 

 of the wood. Ans. $. 



28. A solid which is lighter than water weighs 5 Ibs., 

 and when it is attached to a piece of metal, the whole 

 weighs 7 Ibs. in water. The weight of the metal in water 



