162 



USING MACHINES 



Hunter and Whitman, Science in Our World of Progress, 

 Unit 8; Science in Our Social Life, Unit 8 



Lake, Harley, and Welton, Exploring the World of Science, 

 Chap. 18 



Pieper and Beauchamp, Everyday Problems in Science, Units 

 12, 13 



Powers, Neuner, and Bruner, Man's Control of His Environ- 

 ment, Chap. 16 



Skilling, Tours through the World of Science, Tours 8, 9 



Van Buskirk and Smith, The Science of Everyday Life, Chap. 

 16 



Watkins and Bedell, General Science for Today, Chap. 17 



Webb and Beauchamp, Science by Observation and Experi- 

 ment, Unit 5 



Wood and Carpenter, Our Environment: How We Use and 

 Control It, Topics 2, 3, 10, 11 



Special references 



Bond, The American Boys' Engineering Book 



Bond, With the Men Who Do Things 



Burns, The Story of Great Inventions 



Darrow, The Boys' Own Book of Great Inventions 



WHAT YOU SHOULD AIM TO ACQUIRE FROM 

 THIS STUDY 



1. The ability to recognize and classify the simple ma- 

 chines. 



2. A knowledge of the lever principle and how to 

 make simple calculations involving it. 



3. A knowledge of the work principle. How to cal- 

 culate the work done by, and the efficiency of the 

 various simple machines. 



4. A knowledge of the way to find the mechanical 

 advantage of the various simple machines. 



TEST OF MASTERY OF THE TOPIC 



In your notebook complete the statements, answer the 

 questions, and comply with the instructions. 



1. Work is measured in . 



2. How may the mechanical advantage of a simple 

 straight lever be found? 



3. The efficiency of a machine is found by dividing the 

 by the 



4. The common household food chopper is a combina- 

 tion of what two simple machines ? 



5. Make a list of six household devices which are 

 levers. 



6. What is the mechanical advantage of a single fixed 

 pulley as shown in the diagram in Figure 261 ? 



7. How may the mechanical advantage of a wheel and 

 axle be found ? 



8. Make a list of five household devices which are in- 

 clined planes. 



9. How may the mechanical advantage of an inclined 

 plane be found? 



10. Name two forms of the inclined plane. 



11. The mechanical advantage of a pulley system may be 

 found by counting the . of supporting the 



12. State the lever principle in your own words. 



13. State the work principle in your own words. 



14. Make a list of the uses of simple machines in the 

 automobile. Tell what type each is (lever or inclined plane). 



15. Make a list of five examples of the screw. 



16. What type of simple machine is each of the follow- 

 ing: scissors, knife, automobile jack, gangplank for a .ship, 

 automobile crank, axe, crowbar, chisel, wheelbarrow, shovel, 

 broom, hammer, fish pole, door, gear wheels, fruit jar top? 



TOPIC 3. HARNESSING THE ENERGY ABOUT US 



SUGGESTED PROBLEMS AND QUESTIONS 



1. How is the energy of coal harnessed and con- 

 trolled? 



2. How is the energy of gas and oil made avail- 

 able? 



3. How is the energy of falling water harnessed? 



4. What is the source of the energy about us? 



SUGGESTIONS AND HELPS FOR STUDY 



1. Trace all the types of energy back as far as you 

 can ; for example, the light energy of the bulb comes 

 from the electrical energy of the generator, which 

 comes from the mechanical energy of the steam en- 

 gine, and so on back. 



2. All the various sources of energy which occur 



in nature should be carefully studied, such as coal re- 

 sources, oil resources, water power, wind power, and 

 harnessing the tides. 



3. These problems deal with many common devices 

 such as stoves and burners, electric cooking and heat- 

 ing devices, electric lights and gas light, motors and 

 dynamos, steam engines and turbines and water 

 wheels. Study each one carefully and understand how 

 it converts energy from one type into another. 



4. You may find the following new words and 

 phrases in this study. 



potential energy stored-up energy or energy due to 

 the position of some object. 



kinetic energy energy which a body has because of its 

 motion. 



turbine a special type of wheel used to harness the 

 energy of falling water or steam. 



