84 ENERGY. 



Recapitulation. In this section we have considered 

 the meaning of \Vork and Energy ; the Ele- 

 ments of Work-measure; the Unit of Work, as 

 Foot-pound or K.ilogram-meter ; Horse- 

 power; the relation between Velocity and En- 

 ergy ; a very convenient Formula for Energy ; 

 two Types of Energy, Kinetic and Potential ; 

 the mutual Convertibility of these two Types of 

 Energy ; the Sum of these two as a Constant Quan- 

 tity ; the Pendulum as an Illustration of this Con- 

 vertibility and Constancy; the Indestructibility of 

 Energy. 



REVIEW QUESTIONS AND EXEECISES. 



1. (a.) What is a molecule ? (6.) An atom? (c.) Name the attrao 

 tions pertaining to each. 



2. (a.) Give an original illustration of a physical change, (ft.) Of 

 a chemical change. 



3. (a. ) What is the difference between general and characteristic 

 properties of matter? (&.) Give an illustration of impenetrability, 

 not mentioned in the book. 



4. (a.) Upon what property do most of the characteristic proper- 

 ties of matter depend ? (6.) Name five general and three charac- 

 teristic properties of matter, (c.) Define inertia. 



5. (a.) How does a solid differ from a liquid ? (&.) From a gas ? 

 (c.) How does a gas differ from a vapor ? (d.) What is a fluid ? 



6. (a.) Define dynamics. (&.) What is the difference between 

 statics and kinetics ? (c.) What is the gravity unit of force ? (d.) 

 The kinetic unit ? 



7. (.) Give Newton's Laws of Motion. (&.) Explain the meaning 

 of "parallelogram of forces." (c.) What is an equilibrant ? (d.) 

 Give the law of reflected motion. 



8. (a.) What is the difference between gravity and gravitation? 

 (&.) Give the law of gravitation, (e.) Of weight, (d.) What is 

 meant by centre of gravity ? 



9. (a.) Describe the several kinds of equilibrium. (6.) Upon 

 what does the stability of a body depend? (c.) Show how. (d.) 

 What is the line of direction ? 



