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张力
维基百科,自由的 encyclopedia
张力(英语:Tension)乃是由一拉长、伸展的弦对施力者所做的反作用力。张力与弦的长度平行,方向朝弦
![9 men in the Irish champion tug of war team pull on a rope. The rope in the photo extends into a cartoon showing adjacent segments of the rope. One segment is duplicated in a free body diagram showing a pair of action-reaction forces of magnitude T pulling the segment in opposite directions, where T is transmitted axially and is called the tension force. This end of the rope is pulling the tug of war team to the right. Each segment of the rope is pulled apart by the two neighboring segments, stressing the segment in what is also called tension, which can change along the length of a rope, as it may also change along the grip of each of the tug of war team members.](http://upload.wikimedia.org/wikipedia/commons/thumb/8/83/Tug_Of_War_Tension.png/320px-Tug_Of_War_Tension.png)
由于张力是力的一种,因此它的单位如同力,SI制是kg·m/s²。
张力也存在于弦的内部:若考虑把弦分成两个部分,则张力便是这两个部分互相对彼此作用(拉扯对方)的力。张力的大小决定弦是否断裂,因此张力也是振动(参见vibrating string(英语:vibrating string))的性质之一,而弦乐器则是靠调整弦的张力来调整其音高,并借由震动弦发出声响。
通常将弦绷紧,则张力也会增加。在拉长的长度够小时,虎克定律可以描述这个力的大小。
在狭义相对论中的似弦物体(例如在一些模型中与夸克作用的弦)或现代弦论中的弦里也讨论张力。我们借由这些弦的世界面分析这些弦,它们的能量通常与它们的长度成正比。在这些弦中的张力与它的伸长量无关。
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