action line

• 激励行,作用线

action line的用法和样例：

例句

1. Click on the center dot to rotate the hand around the action line.
   点击中心圆点，沿着作用线旋转手臂。
2. There is an exceptional case, three forces with paralleled lines of action, which will be discussed in Chapter 3.
   三个力的作用线相互平行的例外情况，我们将在第三章讨论。