But,since China is hosting the six party talks and since Beijing is one of Pyongyang's biggest international allies, Baek says North Korea may think more positively on returning to the talks.

VOA: standard.2009.10.05

So, if we think about the force that occurs between a positively and a negatively charged particle, what we have is essentially a Coulomb force, so we can describe this as a force of attraction.

一个带负电的粒子之间，的作用力,这本质上就是库伦力，我们可以把它，描述成一个引力。

麻省理工公开课 - 化学原理课程节选

By the way, I didn't tell you this but I think you know that I picked my origin to be here and measured y positively to be upwards and I called that 15 meters.

顺便说一下,虽然我没明确指出,但我想你们应该都知道,我把原点取在这里,并规定y的正方向朝上,我设把这里的高度为15米

耶鲁公开课 - 基础物理课程节选