第15届中国(厦门)国际投资贸易洽谈会于2011年9月8日上午9时在厦门国际会展中心开幕，历时5天。

如图所示，在一粗糙水平面上有两个质量分别为m₁和m₂的木块1和2，中间用一原长为l、劲度系数为K的轻弹簧连接起来，木块与地面间的滑动摩擦因数为μ。现用一水平力向右拉木块2，当两木块一起匀速运动时两木块之间的距离是（）

补全对话。在横线上填上一个适当的句子，使对话完整、通顺、正确。

W: Good morning, young man.____

M: I feel weak and I've got a bad headache.

W: ____

M: No, I don't have a fever. I have taken my temperature. It's all right.

W: How about your sleep?

M: Terrible! I dream a lot and I always feel tired the next morning.

W: ____

M: I am playing computer games these days. And I play till late at night.

W: I see. You play games too much.

M: ____

W: You should not do that any more first. Then relax a little, have a warm bath and lake this medicine for a week. It will help you.

M: Thanks, doctor. ____ 

W: Three times a day.

M: OK. Thank you. Bye!