24 AXSWEJRS TO PRACTICAL QUESTIONS 



measure. Hence one arm is 2 feet long and the other 8 feet 

 long. PROOF. 50 x 8 = 200 x 2. This is the substance also of 

 the equation P x Pd = W x Wd. 



5. In a lever of the first class, 6 feet long, where should 

 the F be placed so that a P of 1 Ib. will balance a W of 23 

 Ibs.? 



6 feet = 72 inches. 72 *- 24 = 3, the unit of distance. The 

 W must be placed 3 in. and the P 69 in. from the F. PROOF. 

 23 x 3 = 1 x 69 (Prob. 4). 



6. What P would be required to lift a barrel of pork 

 with a windlass whose ajcle is one foot in diameter and 

 handles ft. long? 



P : W : rad. of axle : : rad. of wheel. 



a: : 200 Ibs. : : J ft. : 3 ft. 



x = 33 Ibs. 



7. What sized axle, with a wheel 6 feet in diameter, 

 would be required to balance a W of 1 ton by a P of JLOO 

 Ibs.? 



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



100 Ibs. : 2,000 Ibs. : : x : 6 ft. 



x = T % ft. = the diameter. 



8. What number of movable pulleys would be required 

 to lift a W of 200 Ibs. with a P of 25 Ibs. ? 



W = P x twice the number of movable pulleys ; 



W 

 hence -p- = twice the number of movable pulleys. 



200 -4-25 = 8. 8 -*- 2 = 4 = the number required. 



9. How many Ibs. could be lifted with a system of 4 

 movable pulleys, and one fixed pulley to change the direc- 

 tion of the force, by a P of 1OO Ibs. ? 



W = P x twice the number of movable pulleys. 

 100 Ibs. x (4 x 2) = 800 Ibs. = the W. 



