一宇航员乘坐自动航天飞行器到达一类似地球的星球表面进行科学考察，科考任务结束后，他将星球的自转周期为18小时、同一物块在星球两极时的重力为在星球赤道时重力的 $\frac{27}{26}$ 倍的两个数据星球输入飞行器的航程自动仪中．飞行器自动生成运行轨道，并按此轨道由星球表面P点返回到同步轨道．其中P点和Q点为切点．请问飞行器从椭圆轨道上的P点到Q点需要多长时间？

    Guo Liqin, 24, works as a primary school teacher in a distant area in Yunnan Province. The Internet offers him the latest news and entertainment from the outside world. And many people like him also depends on the online libraries for the free literature(文学) reading.
   A survey in China last year found the online literature is the biggest growth area of Internet entertainment.Reading for free is also popular in other countries. See what solutions other countries are taking.
Public Libraries
   In countries such as Germany, Canada, and the UK, governments pay the authors to have their books in public libraries.
The pay is different from country to country. Some pay according to how many times a book has been borrowed; others pay according to whether the library has bought the book or not.
Google Books
   Google Books allow users to see some free parts before buying them.
The author can choose to make from 20% to 100% of the book’s content(内容) for free reading . But you can see a full view of books that are out of copyright(版权).
E-magazines
   E-magazines are usually about pop culture, and make money through advertisements. The writers are usually paid by the numbers of words they write.
Digital Library
   There are many free online libraries of books which are no longer in copyright.American and European websites offer classic(古典的) literature and non-fiction texts like dictionaries for download in different languages.