Some things are going to slide through, and that's actually a bother. It's a problem.

有些问题会躲过检查，这确实很烦，这是个问题。

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So you can imagine a bead with a wire going through it and the bead can only slide back and forth.

你可以想象一个穿在绳子上的珠子,小珠只能前后滑动

耶鲁公开课 - 基础物理课程节选