MACHINES IN EVERYDAY LIFE 



155 



FIG. 249. LEANING TOWER OF PISA 



REFERENCES FOR FURTHER STUDY 



Caldwell and Curtis, Science for Today, Chap. 7 



Clement, Collister, and Thurston, Our Surroundings, Chaps. 

 2, 6, 18 



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, This Changing World, Chap. 2 

 (part), Chap. 19 (part) ; Man's Control of His Environ- 

 ment, Chap. 15 



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. 16 



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 



TEST OF MASTERY OF THE TOPIC 



In your notebook complete the statements, answer the 

 questions, and comply with the instructions. 



1. Make a list of ten uses of friction. 



2. Make a list of all the hindrances of friction that you 

 can find. 



3. Tell of one attempt at perpetual motion and why 

 it would not work. 



4. When mechanical energy disappears in friction, 



energy appears. 



5. Show three ways in which friction is made use of in 

 the automobile and three ways in which it is a hindrance. 



6. Friction is reduced in machines by means of 



and bearings and by . 



7. What type of energy is being expended in Figure 

 220? Into what form of energy is this being changed? 

 Give another example of this transformation of mechanical 

 energy. 



8. Ball and roller bearings are utilized in reducing fric- 

 tion because is less than friction. 



9. Sand is of value on a slippery railroad or street be- 

 cause it increases and decreases the danger of 



10. The gram is a unit of . 



11. is the amount of matter in a body. 



12. The tendency of a body to remain at rest or in 

 motion is called . 



13. Centrifugal means 



and centripetal means 



14. The force which holds the planets in their orbits is 

 known as . 



15. The of a body is the measure of the pull of 



for that body. 



16. The gram is about of an ounce. 



17. The gram is defined as the weight of of water 



at degrees centigrade. 



18. The _ of a body is its weight per unit . 



19. Two applications of centrifugal force in everyday 

 life are . 



20. Increasing the speed of a moving body is known as 

 while decreasing the speed is known as 



21. Forces never exist but always in . An ex- 

 ample of this is , 



22. Galileo discovered that bodies which have differe 

 fall at the . 



TOPIC 2. THE MACHINES WE USE IN EVERYDAY LIFE 



SUGGESTED PROBLEMS AND QUESTIONS 



1. What is work and how is it measured? 



2. What are the various types of levers and 

 how do they aid us? 



3. How do the different kinds of inclined planes 

 help us do our work more easily? 



4. How may machines be made more efficient? 



SUGGESTIONS AND HELPS FOR STUDY 

 1. Collect and classify as many pictures of 'ma- 

 chines during this study as you can. See the adver- 

 tisements in magazines and newspapers. 



2. The lever and inclined plane are known as~sim- 

 ple machines. All machines, regardless of how com- 

 plicated they may be, are based upon one or both of 

 these simple types. 



3. Mechanical advantage is a term which may con- 

 fuse the beginner. It refers to the number of times 

 greater a load lifted or moved by a machine is than 

 the force which one applies to the machine. For ex- 

 ample, if one can move a 100-pound rock with a lever 

 bar by applying ten pounds of force he has gained an 

 advantage of 10 over the load or resistance. 



4. You may find the following new words and 

 phrases in this study. 



