视频对话：
The edges are worn down from friction.
边缘由于摩擦有所磨损。
Whatever tools they used to cause this leak weren't meant for the job.
不管他们用什么工具造成泄漏，都不是为了工作。
本期学习词汇：
friction
n.摩擦；冲突，不和；摩擦力
例句：
1. Matches are lighted by friction.
火柴由摩擦而生火。
2. The family never had friction.
这家人从来没有摩擦。
3. Sara sensed that there had been friction between her children.
萨拉感觉到她的孩子之间有过争执。
4. The plan is likely only to aggravate ethnic frictions.
这一方案很有可能只会加剧种族冲突。
5. The pistons are graphite-coated to reduce friction.
活塞上涂了一层石墨以减小摩擦力。