Swing, seesaw and pendulum are called simple pendulum movements, which belong to rotation and keep rotating around a fixed point. The swing is centered on the upper bracket and rotates with the rope length as the radius.

Extended data:

Swing principle

Folding mechanical model

If the system composed of man and swing is regarded as a pendulum, the cycloid is fixed at the O point, ignoring the expansion and contraction of the cycloid itself and the mass of the cycloid. Imagine that people quickly squat at the maximum deflection angle and stand at the lowest point. The process of squatting and standing is completed instantly. Squatting and standing of human body lead to the rise and fall of the center of mass of the system, which is equivalent to the change of effective pendulum length.

In this way, the system composed of people and swings is abstracted into a variable pendulum, which is called a variable pendulum model.

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