他们中的一个人解开绕在他腰间的一条绳子。

One of them unwound a length of rope from around his waist.

《柯林斯英汉双解大词典》

他拿了一小段绳子迅速打了个活结。

He took a short length of rope and swiftly tied a slip knot.

《柯林斯英汉双解大词典》

我在绳子上打了个结。

I tied a knot in the rope.

《牛津词典》

We'll give it a name, but by linking that T to that T, we can also figure out the same T must be exerted on this one by Newton's third law, because if this block is the only one that could be pulling this rope with T.

我们先给它命个名,把这个 T 和那个 T 联系起来,利用牛顿第三定律,我们可以知道这个 T 也一定作用在这个物体上,因为如果这个物体是唯一,受到绳子拉力 T 的物体

耶鲁公开课 - 基础物理课程节选