70 GENERAL SCIENCE 



6. What makes the water flow in creeks and rivers? 



7. What causes wagons, electric cars, and sleds to run down hill 

 easily? 



8. Why is it difficult to draw a heavy wagon up a hill? 



9. As far as you know from experience, does the law of the con- 

 servation of energy seem to be true? 



10. Which requires more energy, to walk on the level or up a 

 hill? Why? 



