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(一)如图1所示,甲、乙两个由同种物质组成的匀质小球,在光滑的水平面上作完全弹性正碰。已知两个小球的质量之比 m_甲:m_乙=1:3,碰撞前两个小球的速度方向相反,大小相等,数值为v_0;碰撞后,甲球沿反方向弹回,速度的大小变为原来的两倍,乙球碰撞后静止不动。试问,碰撞中两个小球的最大弹性势能之比为多少?这个问题的概念性比较强。如果我们在平时的教学中不注意经常抓住概念进行分析,而是习惯于讲公式、搞计算,那就很容易犯下面的错误:
(a) As shown in Fig. 1, two homogeneous balls consisting of the same substance in both A and B are fully elastically touched on a smooth horizontal surface. It is known that the mass ratio of two balls is m_A:m_B=1:3. The speeds of the two balls before the collision are opposite, equal in size, and the value is v_0. After the collision, the ball rebounds in the opposite direction. The size of the speed becomes twice that of the original, and the ball B remains stationary after collision. What is the ratio of the maximum elastic potential energy of two small balls in a collision? This question is conceptually strong. If we don’t pay attention to the concept of analysis in the usual teaching, but are accustomed to formulating formulas and doing calculations, it is easy to make the following mistakes: