Part 19

25. (Pg. 37) What number of feet will a heavy body descend in the first second of its fall, and at what rate will its velocity increase?

26. (Pg. 37) What is the difference in the time of the ascent and descent, of a stone, or other body thrown upwards?

27. (Pg. 37) By what reasoning is it proved that there is no difference?

28. (Pg. 38) What is meant by the momentum of a body?

29. (Pg. 38) How do we ascertain the momentum?

30. (Pg. 38) How may a light body have a greater momentum than one which is heavier?

31. (Pg. 38) Why must we multiply the weight and velocity together in order to find the momentum?

32. (Pg. 39) When we represent weight and velocity by numbers, what must we carefully observe?

33. (Pg. 39) Why is it particularly important, to understand the nature of momentum?

34. (Pg. 39) What is meant by reaction, and what is the rule respecting it?

35. (Pg. 39) How is this exemplified by the ivory balls represented in plate 1. fig. 3?

36. (Pg. 40) Explain the manner in which the six balls represented in fig. 4, illustrate this fact.

37. (Pg. 40) What must be the nature of bodies, in which the whole motion is communicated from one to the other?

38. (Pg. 40) What is the result if the balls are not elastic, and how is this explained by fig. 5?

39. (Pg. 40) How will reaction assist us in explaining the flight of a bird?

40. (Pg. 40) How must their wings operate in enabling them to remain stationary, to rise, and to descend?

41. (Pg. 41) Why cannot a man fly by the aid of wings?

42. (Pg. 41) How does reaction operate in enabling us to swim, or to row a boat?

43. (Pg. 41) What constitutes elasticity?

44. (Pg. 41) Give some examples.

45. (Pg. 41) What name is given to air, and for what reason?

46. (Pg. 41) What hard bodies are mentioned as elastic?

47. (Pg. 41) Do elastic bodies exhibit any indentation after a blow? and why not?

48. (Pg. 42) What do we conclude from elasticity respecting the contact of the particles of a body?

49. (Pg. 42) Are those bodies always the most elastic, which are the least dense?

50. (Pg. 42) Give examples to prove that this is not the case.

51. (Pg. 42) All bodies are believed to be porous, what is said on this subject respecting gold?

52. (Pg. 43) What conjecture was made by sir Isaac Newton, respecting the porosity of bodies in general?