24 ANSWERS TO PRACTICAL QUESTIONS 



23. In a lever of the ist class ; what IV will a P of 50 Ibs 

 balance, with a lever 12 ft. long and the F '3 ft. from the IV? 



50 Ibs. : x : : 3 ft. : 9 ft. 

 x = 150 Ibs. 



24. In a wheel and axle, the P=^o Ibs., ^=360 Ibs., 

 diameter of axle = 8 in. Required the circumference of thi 

 wheel. 



P : W :: diameter of axle : diam. of wheel 



40 Ibs. : 360 Ibs. : : 8 in. : x - 72 in. = 6 ft., the diameter of wheel. 

 6 ft. x 3.1416 = 18.85 ft., the circumference of the wheel. 



25. In a wheel and axle the P =-20 Ibs., the ^=240 Its., 

 and the diameter of wheel = \ft. Required the circumference, 

 of the axle. 



20 Ibs : 240 Ibs :: a? : 48 in. 



X = 4 in. (diameter of axle). 



4 in. x 3.1416 = 12.56 in. (circumference). 



26. Required, in a wheel and axle, the diameter of the wheel, 

 the diameter of the axle being 10 inches, P = 100 Ibs. and W 

 I ton. 



100 Ibs. : 2000 Ibs. : : 10 in. : x = 200 in. = 16 a /s ft. 



27. What P would be necessary to sustain a weight oj 

 3,780 Ibs., with a system of 6 movable pulleys and one ropef 



W = P x twice the no. of mov. pulleys. 

 3,780 Ibs. = P x (6 x 2). P = 315 Ibs. 



28. How many movable pulleys would be required to sustain 

 i W 0/420 Ibs. with a P of 210 Ibs. f Ans. I. 



HYDROSTATICS. 



121. i. Why do housekeepers test the strength of lye, by 

 trying whether or not an egg will float on it ? 



The potash dissolved in the water to form lye increases the 

 density of the liquid. When enough has been dissolved to 

 make its specific gravity greater than that of the egg, the egg 

 will float. This becomes, therefore, a simple means of testing 

 the amount of potash contained in the lye. 



