Part 13

9. (Pg. 25) How can the attraction of a mountain be rendered sensible?

10. (Pg. 25) Why cannot two lines which are perpendicular to the surface of the earth be parallel to each other?

11. (Pg. 26) Draw a small figure of the earth to exemplify this, as in fig. 1. plate 1.

12. (Pg. 27) If bodies were not resisted by the air, those which are light, would fall as quickly as those which are heavy, how can you account for this?

13. (Pg. 27) What then is the reason that a book, and a sheet of paper, let fall from the same height, will not reach the ground in the same time?

14. (Pg. 28) What then will be the effect of increasing the surface of a body?

15. (Pg. 28) What could you do to a sheet of paper, to make it fall quickly, and why?

16. (Pg. 28) Inform me how a very dense body may be made to float in the air?

17. (Pg. 28) The air is a real body, why does it not fall to the ground?

18. (Pg. 29) The air is more dense near the surface of the earth, and decreases in density as you ascend, how is this accounted for, and to what is it compared?

19. (Pg. 29) What is it which causes the particles of air to recede from each other, and seems to destroy their mutual attraction?

20. (Pg. 29) Smoke and vapour ascend in the atmosphere, how can you reconcile this with gravitation?

21. (Pg. 30) How would you illustrate this by the floating of a piece of paper on water?

22. (Pg. 30) Does smoke rise to a great height in the air, and if not, what prevents its so doing?

23. (Pg. 30) What limits the height to which vapours rise?

24. (Pg. 30) Of what does smoke consist?

25. (Pg. 30) Air balloons are formed of heavy materials, how will you account for their rising in the air?

26. (Pg. 30) What influence does the air exert, on bodies less dense than itself, on those of equal, and on those of greater density?

27. (Pg. 31) If the air could be entirely removed, what influence would this have upon the falling of heavy and light bodies?

28. (Pg. 31) How could this be exemplified by means of the air pump?

CONVERSATION III.

ON THE LAWS OF MOTION.

OF MOTION. OF THE INERTIA OF BODIES. OF FORCE TO PRODUCE MOTION. DIRECTION OF MOTION. VELOCITY, ABSOLUTE AND RELATIVE. UNIFORM MOTION. RETARDED MOTION. ACCELERATED MOTION. VELOCITY OF FALLING BODIES. MOMENTUM. ACTION AND REACTION EQUAL. ELASTICITY OF BODIES. POROSITY OF BODIES. REFLECTED MOTION. ANGLES OF INCIDENCE AND REFLECTION.

MRS. B.

The science of mechanics is founded on the laws of motion; it will therefore be necessary to make you acquainted with these laws before we examine the mechanical powers. Tell me, Caroline, what do you understand by the word motion?

Caroline. I think I understand it perfectly, though I am at a loss to describe it. Motion is the act of moving about, of going from one place to another, it is the contrary of remaining at rest.

Mrs. B. Very well. Motion then consists in a change of place; a body is in motion whenever it is changing its situation with regard to a fixed point.

Now since we have observed that one of the general properties of bodies is inertia, that is, an entire passiveness, either with regard to motion or rest, it follows that a body cannot move without being put into motion; the power which puts a body into motion is called force; thus the stroke of the hammer is the force which drives the nail; the pulling of the horse that which draws the carriage, &c. Force then is the cause which produces motion.