题目将质量为2m 的长木块静止放在光滑的水平面上,如图1甲所示,一个质量为m的小铅块(可视为质点)以水平初速度 v_0由木块左端向右滑动,到达右端时恰能与木块相对静止.铅块运动中所受的摩擦力始终不变.现将木块分成长度与质量均相等的两段1和2,并紧挨着放在原水平面上,让小铅块仍以初速度 v_n。由木块1的左端开始向右滑动,如图1 Title Long wooden mass with a mass of 2m is placed on a smooth horizontal surface. As shown in Fig. 1A, a mass of small lead (might be seen as a particle) with a horizontal initial velocity v_0 slides from the left end of the block to the right. When it reaches the right end, it can just be relatively stationary with the block. The friction force in the movement of the lead block is always the same. Now the block is divided into two sections 1 and 2 with equal length and mass, and is placed next to the original level. , so that the small lead is still at the initial speed v_n. Slide from the left end of block 1 to the right, as shown in Figure 1.