A special safety net was suspended under the bridge.

VOA: special.2010.07.23

scratch Scratch is a program that you can download for free cs50 net and you will see in problem set 0 0 which will be posted on CS50.nettonight under problem sets in both standard and hacker editions, can you do the--can you--it will walk you through the process of getting this software.

你可以免费下载,今天晚上我会在0,放上习套题,这个习题集有两个版本，习题集可以指导你,如何下载这个软件。

哈佛公开课 - 计算机科学课程节选

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