Work-energy theorem for systems; for rigid bodies, internal forces do no work; energy in gravitating systems; models of internal energy; energy diagrams; equilibria and stability; small oscillations around equilibrium.

• 系统内的功能原理;对于刚体,内力不做功;在重力系中的能量;内能的模型;能量示意图;平衡态与稳态;在平衡态附近的小振动。