POTENTIAL AND KINETIC ENERGY 



61 



in the spring as potential energy. Slowly the change of 

 position of the spring transforms its potential energy back 

 into kinetic energy. 



When a gun is loaded with powder it has potential energy 



due to the composi- __ 



tion of the powder. 

 When the powder is 

 exploded, the poten- 

 tial energy changes 

 into kinetic energy 

 which is imparted to 

 the bullet. The 

 smallest possible 

 amount of nitroglyc- 

 erine has potential 

 energy on account of 

 the arrangement of 

 the atoms in its mol- 

 ecules. When that 

 arrangement is dis- 

 turbed, potential 

 energy becomes ki- 

 netic and an explosion 

 results. 



The sun through- 

 out its existence has 

 been sending vast 

 quantities of energy 

 to the earth. This 

 energy has been 

 mostly in the forms 

 of heat and light. 



Courtesy of Illinois Central Railroad 

 A PILE DRIVER IN ACTION 



The weight or "rain" is lifted to the top of 

 the machine, where it has great potential 

 energy. As it falls, it changes its potential 

 energy into kinetic energy and drives the 

 pile. 



