子弹射入木块的问题是动量守恒定律的典型题,学生解答起来并不很困难,殊不知,其中尚有“陷阱”.题目如图1所示,一质量M=0.8 kg的木块放在光滑水平面上,用钉固定.一质量m=0.2 kg的子弹以v1=200 m/s的速度水平射向木块,传出后速度为100 m/s.若将钉拔去,子 Bullet into the block problem is the law of conservation of momentum typical problem, the students answer it is not very difficult, everyone knows, of which there are “Trap ” The subject is shown in Figure 1, a mass M = 0.8 kg of wood On a smooth, flat surface, fix it with a nail. A bullet of mass m = 0.2 kg is directed towards the block at a velocity of v1 = 200 m / s and a velocity of 100 m / s is reached.