“三根火柴吊八瓶矿泉水”的平衡分析

WHAT UNDERLYING THE EQUILIBRIUM OF THE HANGING EXPERIMENT?

中央电视台第二频道所演示的"三根火柴杆吊八瓶矿泉水"实验,其背后平衡原因引起了热议。笔者对此实验情景建立了简化模型,并进行受力分析,指出结构能保持平衡的关键为悬线上三角(由下火柴杆与其上方悬线所构成)看似在铅垂面内,但实际处于略微倾斜的面内,这导致系统重心位于桌缘里侧,从而桌面提供的支持力能与载荷平衡。笔者针对上述观点设计了实验,通过白色斜线(悬线上三角的侧向投影)与黑色铅垂线的位置对比,使上述观点得到了证实。

The equilibrium mechanism of the hanging-eight-bottles-of-mineral-water-using-three-matchsticks showed on CCTV-2 attracts much attention and hot discussions.A simplified model was proposed and mechanical analysis was carried down in this paper.It is indicated that the pivotal to the equilibrium is that the upper triangle of the suspension lines(constituted by the bottom matchstick and the suspending lines over it)is in a slightly slant plane in fact,though it looks likely to be in the vertical plane.This configuration causes that the center of gravity of the system lies inside the edge of the table,so the normal force provided by the table can make equilibrium with the load.The above-mentioned standpoint was verified by a well-designed experiment.A well-designed experiment,by comparing the positions of the white slant line(the lateral projection of the upper triangle of the suspension lines)and the black vertical line,verified the above-mentioned hypothesis.