334 SOME SIMPLE MACHINES IN THE HOME 



the fulcrum. Another example of such an instrument is 

 seen in the sugar tongs, where we find it is much easier 

 to hold the lump by placing the fingers close to the 

 lump than it is if we were to apply the force far away 

 from it. 



The wheelbarrow is a lever. Almost any boy or girl 

 who lives in the country knows that it is easier to carry 

 a heavy load on the wheelbarrow if the load is placed 

 nearer to the wheel than to the handles (see diagram). 

 The nearer the load can be placed to the wheel, the 

 greater the ease with which the load can be lifted and 

 carried. All of these machines mentioned use a common 

 principle, that of the lever. Let us now study and 

 experiment more closely, and see if we can understand 

 the principles underlying it. 



Experiment. To demonstrate the principle of the lever. 



Materials: Ruler with hole in the center. Weights and string. 



Method: With the lever illustrated find out where a force of i pound 

 must be applied on the force arm to balance the different weights sug- 

 gested in (a), (6), and (c), 

 applied on the weight arm. 

 (a) Place 2 pounds 2 

 inches from the fulcrum. 

 (6) Place 2 pounds 4 

 inches from the fulcrum. 

 (c) Place 6 pounds i 

 inch from the fulcrum. 

 Observation and conclusion: 

 Where will a force of i 

 pound need to be applied 

 to balance the weight in 

 each of the cases (o), (6), 

 From the result of the experiment tell what is wrong an( j ( c ) p c an you work 



out the principle of levers 



by comparing the forces and lengths of arms in each case? What 

 statement will you suggest for the law of levers ? 



F. A . - *-WA. 



4 iV T " " 



(weight) 



