题目

如图所示，用动滑轮把重为80N的物体匀速上提，弹簧测力计示数为48N，则拉力为___      _N．不计摩擦和绳重，动滑轮重为__      _N，这时该动滑轮的机械效率约为      __．        答案：48`   16   83.3%解析:略 Welcome to one of the largest collections of footwear (鞋类) in the world that will make you green with envy. Here at the Footwear Museum you can see exhibits (展品) from all over the world. You can find out about shoes worn by everyone from the Ancient Egyptians to pop stars. Room 1 The celebrity (名人) footwear section is probably the most popular in the entire museum. Stared in the 1950s there is a wide variety of shoes and boots belonging to everyone from queens and presidents to pop stars and actors! Most visitors find the celebrities’ choice of footwear extremely interesting. Room 2 Most of our visitors are amazed and shocked by the collection of “special purpose” shoes on exhibition here at the Museum of Footwear. For example, there are Chinese shoes made of Silk that were worn by women to tie their feet firmly to prevent them from growing too much! Room 3 As well as shoes and boots, the museum also exhibits shoe shaped objects. The variety is unbelievable. For example, there is a metal lamp that resembles a pair of shoes, and Greek wine bottles that look like legs! The Footwear Library People come from all over the world to study in our excellent footwear library. Designers and researchers come here to look up information on anything and everything related to the subject of footwear. 1. Where would you find a famous singer’s shoes? A．Room 1.                              B．Room 2. C．Room 3.                              D．The Footwear Library. 2.All exhibits in each room _____. A．share the same theme B．have the same shape C．are made of the same material D．belong to the same social class 3.Which of the following is true according to the text? A．Room 2 is the most visited place in the museum. B．Researchers come to the Footwear Library for data. C．The oldest exhibits in Room 1 were made in the 1950s. D．Room 3 has a richer variety of exhibits than the other two. 4. The purpose of the text is to get more people to _____. A．do research                           B．design shoes C．visit the museum                        D．follow celebrities