As time increases, the angle increases and we can ask, "How long does it take for the particle to come back to the starting point?"

这个角度随着时间在增加,我们会问,"质点需要多长时间,才能转到起点"

耶鲁公开课 - 基础物理课程节选

How long did it take you to come here?

你到这儿花了多久？

How long实战 - SpeakingMax英语口语达人