问题 选择题

一截面呈圆形的内壁光滑细管被弯成一个半径为R的大圆环,并固定在竖直平面内.在管内的环底A处有一质量为m、直径比管径略小的小球,小球上连有一根穿过位于环顶B处管口的轻绳,在水平外力的作用下小球以恒定的速率从A点运动到B点,如图所示,忽略内外侧半径差别(小球可看作质点),此过程中拉力的瞬时功率变化情况是(  )

A.逐渐增大

B.逐渐减小

C.先减小,后增大

D.先增大,后减小

答案

小球做匀速圆周运动,合外力提供向心力,所以切线方向合力为零,设小球重力方向与切线方向的夹角为θ,

则有:F=mgcosθ,小球上升过程中,先减小,到与圆心等高处θ=0,后增大,

所以cosθ先增大,后减小

所以F=mgcosθ先增大,后减小

根据P=Fv

可知,P先增大,后减小

故选D

阅读理解

Chinese TV shows that describe young people's lives in modern society are crossing the cultural divide and attracting a lot of foreign audiences.

One of the examples is the Chinese TV series "A Beautiful Daughter-in-law Era", a light comedy about a modern Chinese couple.

The TV series was first aired in Shanghai in November 2009. It was dubbed in Swahili and broadcast in east African countries in 2011. Two Kenyan(肯尼亚人) actresses were chosen to do voice dubbing for the two leading roles in the African version of the series. It was a great success in Africa.

Tanzanians(坦桑尼亚人) say that they are able to understand how young Chinese people live happily in modern times and they may be able to find ways to solve their personal problems by watching the series.

Although China is one of the world's most prolific(多产的) producers of TV series, its series are not particularly popular overseas. The popularity of "A Beautiful Daughter-In-Law Era" may serve as an example for Chinese TV producers who want to bring their work to other countries.

In recent years, some TV series that show the lives of people in Chinese cities have achieved some success in the foreign market.

"Go Lala Go!," a TV series that details the adventures of a female office worker named Du Lala, has also started to reach global audiences. The series has been exported to Singapore, Malaysia, the United States and Canada.

"The Chinese dream will be more easily accepted by foreign audiences when it is manifested in small and touching stories," said Meng Jian, a professor at Fudan University.

小题1:What can Tanzanians do by watching the Chinese TV series "A Beautiful Daughter-in-law Era"?

A.They can be chosen to do voice dubbing for the leading roles.

B.They can bring their work to other countries.

C.They can find ways to solve their personal problems.

D.They can be successful at work.小题2:Which of the following is true according to the passage?

A."Go Lala Go!," is very popular in Africa.

B.All the Chinese TV series are popular overseas.

C.Some Chinese TV series that show the lives of people in Chinese countries have achieved some success in the foreign market.

D.Africans can understand the happy lives of Chinese young people in modern times.小题3:What does the word “dub” mean in the third paragraph?

A.表演

B.配音

C.制作

D.拍摄小题4:What’s the best title of the passage?

A.Cultural crossing

B.Chinese TV shows

C.A great success

D.Young people’s lives

选择题