实验一：用弹簧秤拖动木块在水平木板上运动

实验二：用弹簧秤拖动木块在垫有毛巾的水平木板上运动

实验三：用弹簧秤拖动放有砝码的木块在水平木板上运动

回顾课堂上的实验过程回答问题：

在长期生产实践中，人类对各种金属器件的防锈已找到一些比较理想的措施．例如：

（1）农机具采用____ 

（2）自行车的钢圈和车铃是在钢上镀上一层耐腐蚀、耐磨的金属____ 

（3）城市道路护栏的钢铁制品____ 

（4）远洋巨轮船体采用、大型水库的钢铁闸门采用____ 

Visiting Mineral City!

    Mineral City is an interesting place to visit. It is a beautiful little town with many old buildings.

    Take a walk through the center of the town on Main Street. Look first at the Mineral City Hotel. It is on the corner of Main Street and Glenn Avenue. It is about 150 years old and people will stay there. There is an interesting old building across the street from the hotel. This was a post office. Now it is a store for books and videos. There are many places to eat on Main Street. You can get lunch or dinner in one of these places. There is a park between Main Street and Oak Street. You can sit on a bench（长凳）in the park. It is nice and quiet, and you can enjoy the trees and flowers.

    You can also take a walk down Glenn Avenue. Look at the old buildings and interesting little stores on this street.