So, we know this point at one second is 20 meters, so let's just ask one other question and we'll stop.

我们知道该物体上升一秒后到达二十米处,关于这个模型的最后一个问题

耶鲁公开课 - 基础物理课程节选

It's not meant to be more than five, ten minutes of work, but the point of the question, -15, 20 minutes of work, but the point of the question is to motivate people to keep up with the material and do the readings.

几分钟就能完成,这个作业的目的,要十几到二十分钟完成吧,这个作业的目的在于激励大家,跟上课程的进度并去阅读材料

耶鲁公开课 - 心理学导论课程节选