题目

Have you ever heard of Ne Zha? The little boy is a very famous hero in Chinese myth. He flies through the air, riding on the Wind Fire Wheels (风火轮). He also has the Universe Ring (乾坤圈) around his body, the Red Armillary Sash (浑天绫) around his shoulders, and a Fire-tipped Spear (火尖枪) in his right hand._______This summer, a movie called Ne Zha became very popular in China. It created a box office miracle (票房奇迹) of Chinese cartoon. The young boy's story has touched people's hearts._______Most Chinese people see Ne Zha as a kind and great hero.The movie shows in his 一质点从A点开始运动,沿直线运动到B点停止,在运动过程中,物体能以a1=6.4  m/s2的加速度加速,也能以a2=1.6  m/s2的加速度减速,也可以做匀速直线运动.若AB间的距离为1.6 km,质点应该怎样运动,才能使它的运动时间最短,最短时间为多少?