196 THE VITAL PROCESSES 



3. How does potential energy differ from kinetic energy ? 



4. What kind of energy is possessed by a bent bow ? By a revolv- 

 ing wheel? By a coiled spring ? By the wind ? By gunpowder ? 



5. How does decomposing water with electricity store energy ? 



6. Account for the energy possessed by the oxygen of the air and 

 food substances. 



7. Trace the energy supply of the body back to the sun. 



8. Why must both oxygen and food be introduced into the body in 

 order to supply it with energy ? 



9. How may overwork and overexercise diminish the energy 

 supply of the body ? 



10. How may one increase the amount of his energy ? 



PRACTICAL WORK 



Suggested Experiments. i. The change of kinetic into potential 

 energy may be shown by stretching a piece of rubber, by lifting a 

 weight, and by separating the armature from a magnet. 



2. The change of potential into kinetic energy may be shown by 

 letting weights fall to the ground, by releasing the end of a piece of 

 stretched rubber, and by burning substances. 



3. The change of one form of kinetic energy to another may be il- 

 lustrated by rubbing together two pieces of wood until they are heated, 

 by ringing a bell, and by causing motion in air or in water by heating 

 them. If suitable apparatus is at hand, the transformation of electrical 

 energy into heat, light, sound, and mechanical motion can easily be 

 shown. 



4. A weight connected by a cord with some small machine and 

 made to run it, will help the pupil to grasp the general principles in the 

 storage of energy through gravity. A vessel of water on a high support 

 from which the water is siphoned on to a small water wheel will serve 

 the same purpose. 



5. The storing of energy by chemical means may be illustrated by 

 decomposing potassium chlorate with heat or by decomposing water by 

 means of a current of electricity. 



6. Study the transfer of energy from the body to surrounding ob- 

 jects, as in moving substances and lifting weights. 



Fill a half gallon jar two thirds full of water and carefully take the 

 temperature with a chemical thermometer. Hold the hand in the wat^r 

 for four or five minutes and take the temperature again. Inference. 



