WHAT MAKES MAN GO 53 



able to draw a load. The exact amount of energy 

 in this food given to the horse can be accurately 

 computed and the horse like the engine is unable 

 to utilize all of the energy in its food. 



A machine can do no more work than that made 

 possible by the available energy furnished it. The 

 heat produced by the burning coal releases the 

 potential energy stored in the coal for possibly a 

 million years and transforms it into active, kinetic 

 energy. In this change, even though it be dis- 

 tributed to several machines, none of the stored 

 potential energy is lost. 



Chemical energy refers to the amount of work 

 that a molecule can do when it breaks into simpler 

 molecules or atoms. There is nothing distinctive 

 about this form of energy except its source. When 

 two or more atoms are combined into a molecule 

 a certain amount of energy has been used in the 

 process. It will remain in the molecule until part 

 or all of the atoms are released from the molecule, 

 and when they are thus released, a given amount 

 of energy is available to be used in the chemical in- 

 dustries, or to sustain life, or it may be returned to 

 the atmosphere. Energy is thus defined by what 

 it is able to do and our interest centers around the 

 source of the energy that keeps our bodies going, 

 and around the manner in which it is used. 



Possibly the simplest approach to this bio- 

 chemical question "What makes the body go?" in 



