The swing doors had moved in diminishing pendulummovement, and now there was nothing but molecular reverberation, one step up from the imaginary.
弹簧门的摇摆幅度慢慢减小了，从假想的层面上更进一步，现在空气中只剩下了四下回荡的分子运动。
2
The ideal simple pendulummovement is not practical though it is simple, and the practical case comes from the correction and improvement of the ideal case.
理想的单摆运动虽然简单却不实际，实际情况需要在理想情况的基础上进行修正和改进。
3
As an approximate method, with the trigonometric function, the simple pendulum dynamical equation is simplified, and the approximate formula for the period of simple pendulummovement is presented.