![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Tension_figure.svg/langzh-mo-640px-Tension_figure.svg.png&w=640&q=50)
張力
維基百科,自由的 encyclopedia
張力(英語:Tension)乃是由一拉長、伸展的弦對施力者所做的反作用力。張力與弦的長度平行,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)
由於張力是力的一種,因此它的單位如同力,SI制是kg·m/s²。
張力也存在於弦的內部:若考慮把弦分成兩個部分,則張力便是這兩個部分互相對彼此作用(拉扯對方)的力。張力的大小決定弦是否斷裂,因此張力也是振動(參見vibrating string(英語:vibrating string))的性質之一,而弦樂器則是靠調整弦的張力來調整其音高,並藉由震動弦發出聲響。
通常將弦繃緊,則張力也會增加。在拉長的長度夠小時,虎克定律可以描述這個力的大小。
在狹義相對論中的似弦物體(例如在一些模型中與夸克作用的弦)或現代弦論中的弦裏也討論張力。我們藉由這些弦的世界面分析這些弦,它們的能量通常與它們的長度成正比。在這些弦中的張力與它的伸長量無關。
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Tension_figure.svg/320px-Tension_figure.svg.png)