VIII. WORK AND MACHINES 



MEANING OF THE TERMS WORK AND ENERGY 



When a magnet picks up bits of iron, when heat causes 

 water particles to separate into steam as in the locomotive, 

 when the force of gravity causes the falling of bodies, just as 

 when muscular force moves a book from one position to 

 another, work is done. And when work is done by causing 

 motion in matter, energy has been used in doing the work. 



All changes in matter changes in size, temperature, 

 state, form, position are the results of the action of forces. 

 But when it is desired to lay emphasis upon changes in posi- 

 tion, whether of the body as a whole or of the particles within 

 it and of which it is composed, " energy" is said to have been 

 used, and "work" to have been done. Wherever work is 

 done there is expenditure of energy, and the amount of one is 

 a measure of the other. 



It is an accepted belief or "theory" held by scientists that 

 there is no such thing as the destruction of energy, and that it 

 is impossible to create energy. It should be remembered in 

 this connection that the theories of science are based upon 

 what is known to be true, and that likewise they are in accord 

 with known facts insofar as their verification is possible. 

 Theories are thus more than mere opinions. 



The utmost that man can do is either to transfer energy 

 from one body to another, or to transform one kind of energy 

 into some other kind as when electrical energy is converted 

 into heat and light energy. In all such transformations and 

 transferences there is waste in the amount of energy available 

 for man's use, often a large waste, but it is believed that there 



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