沙摆

        沙摆是由限位摆和自由摆连两部分组成。当限位摆的摆动平面和自由摆的摆动平面重合时，沙漏漏出的沙子会画出一条直线，当两个摆的摆动平面不重合时，沙漏所散出的沙子将画出各种图案。沙漏摆动也很有规律。沙摆往复振动的周期主要决定于限位摆的周期。

        沙摆绘制出的图形与其摆绳的长度及两条摆绳合点的位置有关。这里设置了三组参数不同的沙摆，观众可以同时看到三种截然不同的沙摆图案，还可以自己动手调整合点的位置观察图形变化。
    

SAND PENDULUMS

        The sand pendulums consist of two parts: a position-limiting pendulum and a free pendulum. When the swinging plane of the position-limiting pendulum and the singing plane of the free pendulum overlap, the sand leaking from the sandglass will draw out a straight line. When the two swinging planes do not overlap, the sand of the sandglass will draw out various different patterns. Swing of the sandglass follows a strict law. The period for back-and-forth swinging of the sand pendulums is manly determined by the period of the position-limiting pendulum.

       The pattern drawn by the sand pendulums is related with the length of their swinging lines and the position of the common point of the two swinging lines. Sand pendulums with four groups of different parameters are designed here, and you can see four distinct sand pendulum patterns at the same time. You can also adjust the position of the common point to observe change of the pattern.