SIMPLE MACHINES. 



i. 



PRINCIPLES OF MACHINERY. THE LEVER. 



163. What is a Machine?^ machine is a 

 contrivance by means of which the power can be 

 applied to the resistance more advantageously. Its 

 general office is to effect a transformation in the inten- 

 sities of energies, so that an energy of small intensity, 

 acting through a considerable distance, may be made to 

 reappear as an energy of considerable intensity, acting 

 through a small distance, or vice versa. 



164. A Machine cannot Create Energy. 



No machine can create or increase energy. In fact, the 

 use of a machine is accompanied by a waste of power 

 which is needed to overcome the resistances of friction, the 

 air, etc. A part of the energy exerted must therefore be 

 used upon the machine itself, thus diminishing the amount 

 that can be transmitted or utilized for doing the work in 

 hand. 



165. A Common Error. A clear understanding 

 of this fact is very important. Tfiere is a very common 



