请你试一试：用手、桌面及肥皂水探究影响滑动摩擦力大小的因素．

（1）用手按在桌面上，第一次用一定的压力使手滑动．第二次加大手对桌面的压力，使手在桌面上滑动．比较前后两次手掌的感觉有何不同？

（2）用湿手按在桌面上．先用一定的压力使手滑动，然后再用肥皂水沾湿你的手，仍然用同样大的压力使手滑动．比较前后两次手掌的感觉有何不同？

词汇运用：

小题1:When a person in _________ is away, people will do as they like.(权力)                                  

小题2:Do you like the books _________ by Jin Yong? (写)

小题3:The boy turned around and looked at me _________(吃惊) .

小题4:By the end of the ________century, the world population had passed 6 billion. (20)

小题5:A map of the world was _________to me and I was asked many questions. (展示)

小题6:You mustn’t get off the bus until it _______ completely. (停止)

小题7:Her ________patience made her popular among the students. （end）

小题8:China has 4 great ________in ancient times. (invent)

小题9:We suggested not  ________ a boat trip. (take).

小题10:His whole life has been devoted to ________the origin of cancer .(study)