大家知道速度的合成与力的合成都遵循平行四边形定则,而这两种合成又有不同之处,这也是导致学生求速度合成时频频出错的原因,下面就以学生错误率非常高的两道题加以分析.例1.如图1所示,两根细长棒AB与CD分别以垂直于自身的速度v1与v2移动,求交点M的移动速度v?图1图2错解:如图2 We all know that the speed of the synthesis and force are synthesized according to the principle of parallelogram, and the two have different synthesis, which is also led to students frequently asked why the speed of synthesis error, the following error rate is very high two students Example 1. As shown in Figure 1, two slender bars AB and CD move perpendicularly to their own velocities v1 and v2, respectively, to find the moving speed v of intersection M. Figure 1 Figure 2 Malfunction: figure 2