LEVERAGE 



A bent lever (Fig. 15) is often used for peculiar circum- 

 stances, but it acts obliquely and, consequently, with less 

 effect. 



The rules of leverage apply with equal accuracy whether a lever is 

 straight or bent at an angle. Take, for example, the lever shown 

 in Fig. 16. This lever, it will be noted , 

 has one arm bent up at a right angle 

 to the other and a weight hung on 

 the horizontal arm. Imagine a force 

 applied at the end of the vertical 

 arm as shown. It is plain that the 

 weight W times its distance A from 

 the fulcrum is equal to the force F 

 times its distance B from the fulcrum, 

 just as if the lever were in the same 

 straight line. 



FIG. 16. Bell-Crank Lever. 

 Another type of bent lever. 



It is, of course, understood that 

 in all leverage problems the force 

 must always be at right angles to the arm. Therefore, 

 while the weight acts vertically, the force acts in a horizontal 

 direction. The lever is bent up as the direction of the force 

 on the end that is bent is thus changed. 



Questions 



1. Draw a sketch of a hammer removing a nail from a board. 

 Where is the fulcrum? What class lever is it? Why? 



2. Draw diagrams of the three classes of levers and give an 

 example of each kind. 



3. Name some examples of bent levers. 



4. Give three examples of compound levers. 



5. Define fulcrum, force arm, and weight arm. 



6. Will a mechanic who knows why he performs each operation 

 of his trade enjoy his work better than one who does not? Explain. 



