运动员关节扭伤后,医护人员会给他喷涂一种雾状物. 此雾状物是一种极易挥发的液态氯乙烷,用它可让运动员的皮肤迅速冷却,达到麻醉作用。其中用到的物理知识 ____ 

如图甲所示，质量不计的弹簧竖直固定在一压力传感器上，压力传感器是电阻阻值随受到压力的增大而减小的变阻器（压力不超过最大值），压力传感器、电流表、定值电阻和电源组成一电路．压力传感器不受力时电流表示数是I₀．t=0时刻，将一金属小球从弹簧正上方某一高度由静止释放，小球落到弹簧上压缩弹簧到最低点，然后又被弹起离开弹簧，上升到一定高度后再下落，如此反复．整个过程中，不计能量损失，电流表示数I随时间t变化的图象如图乙所示，则（　　）

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在实验室中制取下列气体，所用原理最合理的是

根据短文内容，完成表格。

    Nowadays, more and more teenagers go to study in foreign countries. If you want to do that, here's some information for you.

1  Though you have to spend much money on your education in China, you should know that studying abroad will cost you much more money.

2  You'll have to look after yourself and learn to be independent(独立的). When you say goodbye to your family, you should know that you're not going to travel for a week, but live in a foreign country. You'll have to do everything by yourself even when you are sick. You'll have to get used to the life there.

3  You can learn a foreign language more easily if you live in that country, but you may have some trouble before you can speak the language well.

4   You can make friends from other countries, but there may be some misunderstanding(误会) between you and your friends because of different cultures. Information Card