如图所示是测量小车沿斜面下滑的平均速度的实验．

（1）该实验原理是　 ____　．

（2）该实验目的是练习用刻度尺和 ____测量平均速度．实验时观察到小车沿斜面顶端下滑到斜面底端的运动是 ____直线运动．（选填“匀速”或“变速”）

（3）实验中测得路程s₁上的平均速度为v₁，路程s₂上的平均速度为v₂，路程s₃上的平均速度为v₃．那么，v₁、v₂、v₃的大小关系是　 ____　．（选填＞、＜、=）

根据短文理解选择正确答案。

      A good way to pass an exam is to work hard every day in a year. You may fail （不及格）in the exam if you are lazy for most of the year and then work hard only a few days before the exam. If you are taking an English exam, do not only learn rules of grammar. Try to read stories in English. Speak in English whenever（无论何时）you can. A few days before the exam you should go to bed early. Do not stay up late at night studying. Before you start the exam, read carefully over the question paper（试卷）, try to understand the exact(确切的) meaning of each question. When you have finished your exam, read over your answers. Correct(改正) the mistakes if there are any, and be sure that you have not missed anything out.