THE USE OF THE LEVER 169 



its ends, is called a lever. The point of support is namrti 

 the fulcrum. The advantage of the lever is to obtain a 

 large force by the use of a small force. Let us learn by 

 experimenting. 



Experiment 71. The Use of the Lever. 



Apparatus: Long rule, or stick marked with equal 

 divisions, triangular piece of wood to serve as a fulcrum, 

 set of weights. 



a. Arrange the apparatus as shown in the illustra- 



1111 A ... I ....... 



I - I 



tion. Does it balance? Multiply the smaller weight by 

 its distance from the fulcrum and compare the result 

 obtained by multiplying the larger weight by its distance 

 from the fulcrum. It is not safe to draw your conclu- 

 sions, or form an opinion from one experiment. There- 

 fore place these two weights, and also other weights, at 

 different distances from the fulcrum so that they balance 

 and compare the products as suggested above. What 

 are vour final conclusions? 



This experiment shows you how you can use a small 

 force on the long arm o a lever and exert a large force 

 on the short arm. Notice that the small force has to act 

 a greater distance than tfie large force. You have seen 

 men lift large rocks out of the ground by means of bars 

 of iron called crowbars. You use a lever, or two of them, 



