CHAPTER VI.

67. Show what we mean by the centre of gravity by Figs. 30, 31, and 32.

68. Give the definition of centre of gravity, and explain it. What is shown by Fig. 33?

69. How can we find the centre of gravity of a body? What is said of scales and steelyards?

70. State what is represented by Fig. 38. Illustrate the fact that the centre of gravity seeks always the lowest point.

71. Give the illustrations of the rocking-horse, the swing, etc. What is said of the Laggan stones? Why does an egg lie on its side?

72. Give the illustrations from toys in § 101. Give the illustrations in § 102.

73. Upon what two things does the stability of a body depend?

74. What is said of the stability of bodies whose shapes are represented in Figs. 48, 49, and 50? What of that of a round ball? Why is the pyramid the firmest of all structures?

75. What is the relation of upright position to stability? What is stated of the tower of Pisa?

76. Give the familiar illustrations in § 105. What is said of the support of the centre of gravity in animals?

77. What is said of the skill exercised in walking? What of the mode of walking in a child? What of the motions of the centre of gravity in walking?

78. What is said of the walking of a man with wooden legs? Illustrate the management of the centre of gravity in different attitudes. Describe and explain the way in which one rises from a chair.

79. State and explain the wager case. What is said of unstable equilibrium? Give illustrations.