LEVERAGE 



__ /r \ f 



free ends of other lovers. Large scales used in weighing 

 luggage, bricks, wagon loads, and so on, consist of an arrange- 

 ment of compound levers, 

 whereby the arm on one 

 side of the fulcrum is 

 lengthened and the arm 

 on the other side is short- 

 ened. The brake rig- 



FIG. 14. Compound Levers. 



ging on locomotives and cars is a familiar example of a 

 compound lever. 



Two or more levers joined and working together (Fig. 14) il- 

 lustrate this principle of leverage. Here a weight suspended on a 

 hook at W causes the end of the second lever P to swing downward. 



35. Problems in Compound Leverage. Problems in 

 compound leverage are easily reduced to repeated cases of 

 simple leverage, the force at the end of the first lever being 

 the weight or force applied to the second lever, and so on 

 through any number of levers. 



As an example: If the force at W in Fig. 14 is 12 Ibs., what is 

 the force at P? 



For the first lever the force pushing up at the end of the long arm 



12 X 3 



= 3 Ibs. For the second lever it is: 



3 X3 



12 12 



While the safest way is always to figure each lever as a simple 

 lever, as just explained, a shorter method of obtaining the answer 

 is as follows : 



Multiply the weight by the continued product of the short arms of 

 all the levers, and divide this by the continued product of the long 

 arms of the same levers. 



