ENERGY SUPPLY OF THE BODY 



IQI 



the oxygen, but are separated chemically from it.) On 

 account of this relation they have potential energy the 

 energy derived through the plant from the sun. When a 

 person eats the food and breathes the oxygen, this energy 

 becomes the possession of the body. It is then converted 

 into kinetic energy as the needs of the body require. 



From the Sun to the Cells. It thus appears that the 

 body comes into possession of energy, and is able to use 

 it, through a series of transferences and transformations 

 that can be traced back to the sun. 1 Coming to the earth 

 as kinetic energy, it is transformed into potential energy 

 and stored in the compounds of plants and in the oxygen 

 of the air. Through the food and the oxygen the poten- 

 tial energy is transferred to the cells of the body. Then 

 by the uniting of the food and the oxygen at the cells 

 (oxidation), the potential becomes kinetic energy and is 



1 Energy, like matter, can neither be created nor destroyed, 

 ever, be transferred from one body to another and 

 transformed from one form to another form. When- 

 ever work is done, energy is transferred from the body 

 doing the work, to the body upon which the work is 

 done. During this process there may, or may not, be 

 a transformation of energy. In turning a grindstone, 

 kinetic energy is passed to the stone and used without 

 transformation, but in winding a clock, the kinetic energy 

 from the hand is transformed into potential energy in 

 the clock spring. Then as the clock runs down this is 

 retransformed into kinetic energy, causing the movements 

 of the wheels. 



Not only is kinetic transformed into potential energy 

 and vice versa, but the different forms of kinetic energy 

 (heat, light, electricity, sound, and mechanical motion) 

 are readily transformed the one into the other. With 

 suitable devices, mechanical motion can be changed into 

 heat, sound, or electricity; heat into motion and light; 

 and electricity into all the other forms of energy. These 



It can, how- 



FIG. 84. Simple 

 apparatus for illus- 

 trating transformation 



of energy. Potential 



transformations are readily explained by the' fact that energy is converted 

 the different varieties of kinetic energy are but different i nto heal ant l heat 

 forms of motion (Fig. 84). into motion. 



