在高三复习中,下面这道关于物体动态平衡的问题,用常规方法很难做出判断,用数学方法则显得很简洁。题目如图1所示装置,用两根细线拉住一球。现保持两绳间的夹角不变,把整个装置顺时针缓慢转过90°,则在转动过程中,OA、OB的拉力大小分别怎样变化?分析该题中有两个力的大小、方向 In the third year of review, the following question about the dynamic balance of objects is difficult to judge by conventional methods, and it is very simple using mathematical methods. The problem is shown in the device shown in Figure 1, with two thin wires pulling a ball. Now keep the angle between the two ropes unchanged, and rotate the whole device clockwise slowly through 90°. Then, how do the tension forces of OA and OB change during the rotation? Analyze the size and direction of the two forces in the problem.