66 



Is it true that P X force arm equals W x weight 

 arm ? 



What are some of the uses of the lever ? 

 Levers are not necessarily straight. Suppose Figure 52 a 

 represents an ordinary lever with its fulcrum at the place 



indicated by the dash. If 

 now the shorter end is curved 

 as in Figure 52^, we still 

 have a lever. Such a lever 

 is represented by an ordi- 

 nary claw hammer (Fig. 53). 

 In the claw hammer a 

 force applied by the hand at 

 c removes the nail at d. 

 But in order to draw the nail 

 out one inch, the hand must 

 move 4 times that distance, provided the arms of the lever 

 are as 4 to I ; that is, provided the handle of the hammer is 

 four times as long as the shorter curved end. 

 Give another illustration of a curved lever. 



fb 

 FIG. 53. Claw hammer as a lever. 



EXPERIMENT 56. THE INCLINED PLANE 



Prop a smooth board 

 in such a way that the 

 height AB is approxi- 

 mately equal to \ the 

 length of the board 



(Fig. 54). 



Fasten a roller (a 

 tomato can with strings 

 glued to it will do) to a 



FIG. 54. The inclined plane. 



