In the president's motorcade, a vehicle carrying photographers collided with an ambulance as it traveled to the event, and was struck by a falling tree limb as it returned.

VOA: standard.2010.02.06

Conversely, if you get an answer and it doesn't seem to make sense, then you've got to go back and ask, am I violating some of the assumptions, and here you will find the assumption that the particle had that acceleration a is true as long it's freely falling under gravity but not when you hit the ground.

反过来说,如果你得到一个结果,发现似乎是错的,那么你就应该回过头来问问自己,我是不是违反某些前提了,这个模型中,你就发现,只要质点在重力作用下自由下落,质点具有加速度a的前提是正确的,但是落地后就不成立了

耶鲁公开课 - 基础物理课程节选

British commanders say this Operation is making good progress, but in Afghanistan as a whole it has been a tough month, and in Britain public opinion-polls indicate public support is falling.

VOA: standard.2010.08.04