主要区别-力矩与耦合

在物理学中，力矩和耦合这两个术语与在物体上引起转动效应的力有关。力矩和力偶之间的主要区别在于，在力矩中，由于产生转动效应的力，可能存在也可能不存在合力，而在力偶中，则没有合力。

什么是瞬间(moment)？

Technically, a moment is a combination of a physical quantity and a distance. However, in this article we use the term “moment” to mean the “torque” that an object experiences due to a force. The torque  about any point due to a force  is given by the cross product between  and the vector  drawn from the point we are interested in, to the point where force is applied:

Defining Torque

力矩的大小可以由力与垂直于力作用线的距离的乘积给出：

Finding the magnitude of torque using perpendicular distance to the line of action of force.

所以在这种情况下，

什么是夫妇(couple)？

A couple describes a system where there is a resultant torque by a system of forces, without there being a resultant force. Let us look at a system where a pair of forces, each with a magnitude  , separated by a perpendicular distance  form a couple.

由于净力必须为0，因此力的作用方向必须相反，并且它们的大小相同。我们在下面计算这些力产生的扭矩。

A couple

Let us c***ider the torque at . This is the midpoint between the two forces. Each force contributes to a clockwise turning effect about this point. So, the total (clockwise) moment about O is:

Note that for a couple, the resultant torque is always the same regardless of about which point the moments are taken. In the above example, we can confirm this by taking the moment about point  . In this case, the torque by the force at  is 0 (because the distance to the force is 0). Then, the net torque is only due to the force at the other end of the object. This force is at a perpendicular distance  away, so the torque is:

情侣的例子包括手在方向盘上施加的力、螺丝刀头上的力和作用在自行车踏板上的力。

The force exerted by hands on a steering wheel 形式a couple

瞬间(moment)和夫妇(couple)的区别

合力：

一个力矩可能会也可能不会伴随一个合力。

一对夫妇并不伴随着合力。

力的作用：

只有一个力才能产生力矩。

但是，一个力不能产生一对。

Image Courtesy:

“Hands on a steering wheel.” by Vernon Chan [CC BY 2.0], via Wikimedia Comm***