254 Our Surroundings 



6. What sort of a machine is a crowbar? Can heavier work be done 

 with a long-handled bar or with a short-handled bar? 



7. Where would you place a heavy weight in a wheel-barrow in order 

 to wheel it most easily? 



8. Describe the inclined plane. Name several simple machines which 

 make use of it. 



9. Why should the surface of an inclined plane be smooth and hard? 



10. Describe the wheel and axle and its use. 



11. What is the advantage of rollers or casters under heavy objects? 



12. How does your own body illustrate the principles of the lever? 



13. Name several machines used in or about your home. State the simple 

 machines involved in each. How does each save human labor? 



14. Look at an engine or study a diagram of one. What simple machines 

 do you find used in it? 



15. Name several machines which have contributed much to human 

 progress. 



16. Is it true or false that a machine makes energy? 



17. Suggest several activities in which you have to overcome friction. 

 Suggest several ways in which you make use of friction. 



PROJECTS 



1. Construct a movable pulley. Experiment with it, using known weights 

 and a spring scale. Record your findings. 



2. Locate a lever of each class in your body and explain its use. 



3. Make labeled diagrams to show how the principle of the lever is used 

 in standard beam scales. 



4. Secure a spring scale and a flat bottomed box. Fill the box in turn 

 with different substances, and determine the pull necessary in each 

 case to hold it stationary on a wooden inclined plane and to draw it 

 up the plane. Repeat the experiments after coating the plane and the 

 base of the box with other substances, such as cloth or sandpaper. 

 Record your findings and conclusions. 



OUTDOOR OBSERVATION 



1. Study some large machine at work such as a steam shovel or a har- 

 vesting machine. Make simple labeled sketches to show what ele- 

 mentary machines are used in it. 



2. List six tools or machines seen on your way to school. Observe what 

 simple machine forms are made use of in each. 



REFERENCES 



Introductory Physics Higgins 



Boys' Own Book of Inventions Darrow 



