A Pentagon spokesman says most of the Marines will be based on three ships anchored offshore, with a small security force protecting equipment and supplies onshore at night.

VOA: standard.2010.01.19

So, a massless body cannot have a net force on it, because the acceleration of the rope cannot be infinite.

所以没有质量的物体不会受到力,因为绳子的加速度不可能是无穷大

耶鲁公开课 - 基础物理课程节选

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

"Because as I speak to you, Nigeria is not yet fully ready, so I hope some of this will be passed on to Nigeria to force them to be ready in time."

VOA: standard.2009.10.22

That force is scheduled to be reduced from nearly by next October,and to zero by the end of 2011, although Secretary Gates said Friday there could be a follow-on agreement for some U.S.troops to stay, particularly elements of the Air Force.

VOA: standard.2009.12.12