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在日常生活中,挑着东西走路的人,一般都选用软扁担。随着挑担者有规律前进的步伐,物体上下作有规律的振动,扁担两端随之上下弯曲,挑担者并不感到很累。这是为什么呢?我们知道,当挑担者以均匀的步伐行进时,软扁担两端所挂重物作受迫振动,硬扁担两端所挂重物作受迫振动就不明显。设扁担的质量与重物相比可以忽略,所挂重物的质量各为m,若选用硬扁担挑重物,肩受到的压力N_1=2T_1=2mg(T_1及下面的T_2为悬绳对扁担的拉力) 即当选用硬扁担挑重物时,肩受到的压力始终为两重物的重量。若选用软扁担挑重物,重物在竖直方向上下作受迫振动的过程中,其加速度方向时而向上,时而向下。如图(1)、(2)。
In daily life, people who are lugging and walking generally choose soft pole. As the picker has a regular pace of progress, the body up and down to make a regular vibration, pole at both ends will be bent up and down, the picker does not feel tired. What is the reason? We know that when the bearers walk at even paces, the heavy objects on both ends of the soft pole are forced to vibrate, and the forced vibration of the heavy objects at both ends is not obvious. Set the quality of the pole is negligible compared with the heavy objects, the quality of the heavy objects are m, if the choice of hard pole heavy load, shoulder pressure N_1 = 2T_1 = 2mg (T_1 and the following T_2 for the rope on the pole Of the pull force) that is elected with a hard pole load, the shoulder pressure is always the weight of two weights. If you choose soft slab heavy load, heavy objects in the vertical direction for forced vibration up and down, the direction of its acceleration from time to time, sometimes down. As shown in (1), (2).