“测定液体压强与深度关系”是一个很重要的实验。但是，这个实验做起来较为困难，主要有以下几个问题：（1）取材不易，平底试管难以搞清，即使有，不是粗就是细，不合适，另外一般学校的天平较少，不能分组做；（2）成功性小，学生每次往试管里装沙或多或少，因而不是下沉就是倾斜，不呈竖直状态，往往实验做得半途而废；（3）费时多，由于每加一次沙都要用天平称量，步 The “determination of liquid pressure versus depth” is a very important experiment. However, this experiment is more difficult to do, mainly the following problems: (1) difficult to obtain, flat test tubes difficult to find out, if there is, not thick or thin, inappropriate, and the average school balance is less, can not be grouped to do (2)Successfulness is small. Each time the student loads more or less sand into the test tube, it is not sinking or tilted. It is not in a vertical state. Often experiments are done halfway. (3) Time-consuming, because each time Sand must be weighed with a balance, step