THE MECHANICAL POWERS. 281 



crum and divide the product by the distance of the weight 

 from the fulcrum. 



EXAMPLE. What weight will a power of 250 Ibs. 10 

 feet from the fulcrum raise, the weight placed 20 inches 

 from the fulcrum ? 



SOLUTION. 250 Ibs., the power, x 120 inches, its distance 

 from the fulcrum, 30000 -=-20 inches, distance of weight 

 from fulcrum, =1500 Ibs. Ans. 



The GENERAL RULE, therefore, for ascertaining the rela- 

 tion of power to weight in a lever, is : the power applied, 

 multiplied by its distance from the fulcrum, is equal to the 

 weight multiplied by its distance from the fulcrum. 



The pressure upon the fulcrum equals the sum of the 

 weight and power. 



NOTE. It must be remembered that, according to the 

 foregoing rules and examples, the weight and force are made 

 by the introduction of the lever to equal or balance each 

 other. Hence, to get at their practical value, we must either 

 shorten the short arm, or lengthen the long arm of the lever, 

 add to the power, or deduct from the weight, to such an 

 extent as each may judge for himself expedient under the 

 circumstances. 



