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现行普通高中物理课程标准实验教科书选修3-5(人民教育出版社,2010年4月第3版)第23页讲述了反冲运动中火箭喷气后增加的速度。设火箭在飞行时极短时间Δt内喷射出的气体质量为Δm,相对于喷气前火箭的速度是u,火箭一次喷气后增加的速度是Δv,以喷气前的火箭为参考系,得出方程mΔv+Δmu=0①。笔者认为教材中将气体相对于火箭喷气前的速度设为u是不恰当的,因为一般说来,火箭喷出的气体相对于火箭的速度u
The Current Ordinary High School Physics Curriculum Standard Experiment Textbook Elective 3-5 (People’s Education Press, April 2010, 3rd Edition) Page 23 describes the rate of increase after a rocket jet in a recoil movement. Assuming that the mass of gas ejected from the rocket during the flight Δt is Δm, the velocity of the rocket relative to that before the jet is u, and the velocity of the rocket after the first jet increases by Δv. The rocket before the jet is taken as the reference system to obtain the equation mΔv + Δmu = 0①. I believe that the teaching materials will be relative to the gas jet rocket speed before the u is not appropriate, because in general, the rocket gas ejection speed relative to the rocket u