假设原跑道100m，李刚过终点时时间为10sV李＝s/t＝100m/10s＝10m/sV张＝s/t=(100m-10m)/10s=9m/s改变后t李＝s/v=110m/10m/s=11st张＝s/v=100m/9m/s=11.1s又11s＜11.1s所以李刚先到达终点
