对称显示出物质世界的和谐、优美和均衡．用对称分析问题可以培养发散性思维,也可以使一些复杂问题简化． 1．运动对称如竖直上抛运动、简谐运动等．例1 弹簧振子以O点为平衡位置做简谐运动,从某次经过O点开始计时,振子第一次到达M点用了0．3s,又经过0．2s第二次通过M 点．则振子第三次通过M点,还要经过的时间可能是( ) Symmetry shows the harmony, grace and balance of the material world. Symmetric analysis problems can develop divergent thinking, but also can simplify some complex issues. 1. Motion symmetry such as vertical throwing motion, simple harmonic motion, etc. Example 1 The spring oscillator performs a simple harmonic motion with the O point as the equilibrium position. From a certain point, it starts timing at point O. The first time the vibrator reaches M is 0.3 s, and the second time passes 0.2 s through M point. Then the vibrator passes the M point for the third time, but the elapsed time may be ()