火箭运动微分方程讲法的探讨

STUDY OF TEACHING METHOD OF ROCKET MOTION DIFFERENTIAL EQUATIONS

文章针对大学物理教材对火箭运动微分方程的讲法,根据动量定理讨论了火箭系统动量表达式的导数,提出了一个容易引起学生误解的矛盾问题;然后,介绍了理论力学教程中质量流动动力学方程,并利用质量流动问题讲解火箭运动微分方程,避免了矛盾的出现;最后,通过两种讲解方法的分析比较,总结给出了火箭系统动量的一般表达形式,能正确表达火箭系统的动量及其导数.利用动量定理直接对该式求导的讲法不仅避免了矛盾,而且解释了引起学生误解的原因.

In this paper, the teaching method of rocket motion differential equations was stud- ied, and the derivative of rocket system motion expression was also studied based on momen- tum theorem. This paper described a contradiction problem that students tend to misunder- stand and then introduced the mass flow kinetic equation in theoretical mechanics tutorial. The solution of mass flow problem was used to avoid the contradiction. Through analysis and com- parison between two teaching methods~ the general expression of rocket system momentum was given in the end, which can correctly represent rocket system momentum and its deriva- tive. The teaching method that directly finds derivation of this general expression not only a- voided contradiction but also explained the reasons that caused students＇ misunderstanding.