第一届全国中学生力学竞赛计算题第一题是具有不同加速度物体的动力学问题。原题如下: 有一倾角为30°的直角三角形光滑劈,其质量为4.5千克,置于光滑的水平面上,将质量为2千克的物体放在光滑的斜面上,如图1,当m沿M自由下滑时,劈将沿水平方向滑动,求M滑动的加速度a。方法一分别作出m和M的受力分析图如图2(a)所示.图中R是水平面对劈M的支持力。坐标系 The first question in the first National Middle School Student Mechanics Contest was the dynamics of objects with different accelerations. The original question is as follows: There is a right-angled triangular smooth rake with an inclination of 30°, with a mass of 4.5 kg. Placed on a smooth horizontal surface, a mass of 2 kg is placed on a smooth slope, as shown in Fig. 1, when m is along M. When it slides freely, the gill will slide in the horizontal direction, seeking the acceleration a of the M sliding. The first method and the second force analysis chart for m and M are shown in Figure 2(a). In the figure, R is the support force for horizontally facing 劈M. Coordinate System