The momentum of the cluster as a whole would not change if there are no external forces on the system, 0 if the net sum, the total external force, is zero.

星云的动量,作为整体是不变的,若无外力作用于系统，如果外力总和为。

youdao

The net energy is the sum of the repulsive and the attractive.

净能量是排斥能，和引力能的总和。

youdao

And so the net, the sum of all forces on that object there is no net force on that wheel but there is a net torque, and that's why it's going to precess.

所以综合，物体受的所有力，车轮不会受到净力，但是有一个，净作用力，那就是我要推进的。

youdao

So that means if we add up all of the formal charges within the molecule, what we would expect to see is that they sum up to give a net charge of negative 1.

那么这就意味着如果我们把这个分子中,所有的形式电荷加起来，我们应该会看到它们加起来,之后得到的净电荷量为负一。

麻省理工公开课 - 化学原理课程节选

The net energy is the sum of the repulsive and the attractive.

净能量是排斥能,和引力能的总和。

麻省理工公开课 - 固态化学导论课程节选

I am going to say if that electron is to stay in its orbit, that is to say it doesn't flee the atom, it doesn't collapse under the nucleus then the sum of the forces on the electron must be zero No net force. And so that will be the sum of a dynamic force plus an electrostatic.

如果电子会保持在它的轨道上运行,既不脱离原子的话，它就不会由于原子核对它的吸引力而被瓦解掉,电子所受的合力一定为零,由于没有合力,所以电子所受力为动态力和静电力的总和。

麻省理工公开课 - 固态化学导论课程节选

Ireland, Portugal, Cyprus and Spain also all owe investors abroad a net sum of 80-100% of GDP (the gross debt is much larger).

ECONOMIST: The euro

Using stock charts to interpret price and volume action on the major indexes and on leading stocks is an invaluable way to assist with market direction analysis, because charts show the net sum of all the bulls and bears in an index or in a stock.

FORBES: What Do You Do Now That Stocks Have Bounced?

In sum, net neutrality and stopping online piracy are very different issues.

FORBES: SOPA Opponents' Bogus Net Neutrality Comparisons