题目

What might the future be like? Here are some predictions: things to come, things to go. The last few days of every year in big cities in China, when everyone returns home, havebeen the worst headaches for millions of Chinese. More than 2 billion people travel at the same time, making getting travel tickets and the journey difficult. But in 28 years, Spring Festival travel may not be a problem at all. China plans to build more than 120,000 kilometers of railway and a fast transportation network that will serve 90% of the population by 2020. And because most of China will be cities, people will 如图，在Rt△ABC中，∠C＝90°，AC＝6，BC＝8．动点P从点A开始沿折线AC－CB－BA运动，点P在AC，CB，BA边上运动的速度分别为每秒3，4，5个单位．直线l从与AC重合的位置开始，以每秒个单位的速度沿CB方向移动，移动过程中保持l∥AC，且分别与CB，AB边交于E，F两点，点P与直线l同时出发，设运动的时间为t秒，当点P第一次回到点A时，点P和直线l同时停止运动．（1）当t＝5秒时，点P走过的路径长为_________；当t＝_________秒时，点P与点E重合；（2）当点P在AC边上运动时，连结PE，并过点E作AB的垂线，垂足为H. 若以C、P、E为顶点的三角形与△EFH相似，试求线段EH的值；（3）当点P在折线AC－CB－BA上运动时，作点P关于直线EF的对称点Q．在运动过程中，若形成的四边形PEQF为菱形，求t的值．