题目

Our views towards life change over the time. When I was around five years old, I was in a car accident. At that time, I did not realize the seriousness of it and how lucky I was to still be alive. As I look back to think what happened on that night, I now realize how lucky my family members and I were to not have gotten serious injuries.The day of the accident started out great. My brother, Troy, and I had spent the night before at JoAnn’s house, with Heather, and JoAnn’s husband Gary. The next day we spent playing inside the house, because it was cold, windy and rainy outside. At night, J18．如图所示，在光滑水平地面上有一质量为2m的长木板，其左端放有一质量为m的重物（可视为质点），重物与长木板之间的动摩擦因数为μ．开始时，长木板和重物都静止，现在给重物一初速度v0，已知长木板撞到前方固定的障碍物时，长木板和重物的速度恰好相等，长木板与障碍物发生碰撞时不损失机械能，重物始终不从长木板上掉下来．（1）求长木板与前方固定的障碍物相撞时的速度的大小；（2）求长木板撞到前方固定的障碍物前运动的位移大小；（3）求重物最终在长木板上相对滑动的距离大小．