Swing Mechanical Model

If the system composed of man and swing is regarded as a pendulum, the cycloid is fixed at point O, and the expansion and contraction of the cycloid and the mass of the cycloid are ignored. Suppose a person squatted quickly at the maximum deflection angle and stood up quickly at the lowest point, and the process of squatting and standing was completed in an instant. The squatting and standing of the human body lead to the rise and fall of the center of mass of the system, which is equivalent to the change of the effective pendulum length. In this way, we abstract the system composed of man and swing into an original pendulum with variable pendulum length, which is called the original pendulum model with variable pendulum length. The path taken to complete the first swing of the center of mass is a-d-e-b-c, the equivalent pendulum length oa=ob=oc=l1 when a person is standing, and the equivalent pendulum length od=oe=of=l0, l0>ll when a person squatting.