通过追根溯源,找出该高考题的出处及演变过程,分析了题目及官方答案存在的瑕疵及修改意见,并应用动量定理和变质量体系的运动方程两种方法求解. By tracing the source, find out the origin and evolution of the college entrance examination questions, analysis of the problems and official answers flaws and the views of modification, and the application of momentum theorem and variable mass system equations of motion two methods to solve.