The group says it could be hard to stop experimental organisms from entering the natural environment.

VOA: special.2010.07.20

But another possibility is once you do something it's kind of hard to stop.

但也有可能是因为,婴儿很难使自己的惯性动作停下来

耶鲁公开课 - 心理学导论课程节选

You need to stop making me work so hard.

你不要再让我这么拼命地工作了。

so that 实战 - SpeakingMax英语口语达人

Also, there's a hard stop so both people know the date is going to end.

BBC: Should lunch breaks be mandatory?

On the day of the shooting, it was decided that three unmarked police cars would form a box for the hard stop.

BBC: Azelle Rodney death: Police 'shot suspect six times'

Mr Rodney of west London was killed on 30 April 2005 within seconds of the car he was in being brought to a "hard stop", the inquiry has heard.

BBC: Azelle Rodney shooting: Police video shows car pursuit