题目

Philadelphia offers a ton of attractions that are suitable for people of every age and here are some family-friendly attractions.Spruce Street Harbor ParkSpruce Street Harbor Park, one of the best urban beaches in America, is an outdoor heaven on the Delaware River waterfront. Visitors can relax in a hammock, play on the playgrounds, and play games like table tennis and giant chess. Don't miss out on the park at night, when colorful LED lights' hanging from treetops make the entire area bright.Blue Cross RiverRinkOffering ice skating in the winter and roller skating in the summer, Blue Cross R（2007?成都模拟）（1）图左中已经画出了入射光线和折射光线．请画出相对应的反射光线．（2）为使图右中所示的杠杆保持静止，在A点作用了一个力F，力的方向不同，则大小也不同．请画出当力最小时，F的示意图．