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《物理教学》1979年第2期刊载的《莫斯科大学入学试题(物理)摘选》第1题,是一道求两个物体运动何时距离最小的好题目.现除原解(解法1)外,再介绍两种解法,供教学中参考.〔题目〕点P_1以速度v_1由A向B作匀速运动,同时点P_2以速度v_2由B向C作匀速运动(见图1).距离AB=ι_0锐角ABC等于a_0试求t等于多少时,点P_1和P_2之间的距离r最短,并求该距离.
The first question of “Selection of Moscow University Entrance Test (Physics)” in the 2nd issue of Physics Teaching, 1979, is a good topic for finding when the distance between two objects moves is the smallest. Now that the original solution (solution 1) , and then introduce two solutions for reference in teaching. (Problem) point P_1 with speed v_1 from A to B for uniform movement, while point P_2 with speed v_2 from B to C for uniform movement (see Figure 1). Distance AB = Ι_0 acute angle ABC is equal to a_0 try t equal to how much, the distance r between point P_1 and P_2 is the shortest, and seek this distance.