Dr.Rwagacondo says if children get sick, they don't go to school and fall behind scholastically.

VOA: standard.2009.04.25

That's because the ideas of physics don't fall into 75-minute segments and sometimes they spill over a little bit.

因为物理的知识不是死板的75分钟课程,所以我会有时候做一些微调

耶鲁公开课 - 基础物理课程节选

you have to like keep working it until... so that you don't fall behind.

你就要不断地工作学习直到……这样你才能不落后。

都是天才 - SpeakingMax英语口语达人

Of course, this all looks and sounds really scary, but if a 1000 robot-obsessed Japanese scientists haven't been able to build any normal-looking androids this big that don't fall over and don't require a gigantic power backpack of batteries, it's tough to believe that three crafty Bulgarians will do it.

ENGADGET: Prepare to be terminated: The Kibertron

"We want the supply of bags in advance so we don't fall short, " he said.

WSJ: Indian Fiber Weaves a Crisis

It's certainly one way to ensure you don't fall victim to volcanic ash.

BBC: Holidaymakers on the beach in Blackpool