问题 填空题

如图所示,人重600N,木块重400N,人与木块、木块与水平面间的动摩擦因数为0.2,不计绳、滑轮的重力及绳与滑轮间的摩擦,现在人用水平力拉绳,使它与木块一起向右作加速度a=1m/s2的匀加速直线运动,则人拉绳的力是______N,人受的摩擦力大小为______N,方向______.

答案

由人重600N,木块重400N,可知人的质量M=60kg,木块的质量m=40kg

对人和木块整体受力分析知其受绳的拉力,摩擦力,由牛顿第二定律得:

2F-μ(M+m)g=(M+m)a

2F-0.2×1000=100×1

解得:F=150N

对人受力分析,其受绳的拉力,摩擦力,由牛顿第二定律:

F-f=Ma

150-f=60×1

解得:f=90N

方向水平向左

故答案为:150;90;水平向左

单项选择题 A1型题
阅读理解

D

For Chinese, it’s a time for dragon boat racing and Zongzi(粽子). But across the Yellow Sea, South Korea, wrestling(摔跤)and swing play are the highlights. However, both events go by the same name---the Dragon Boat Festival---which falls on May 5 of the lunar calendar.

One festival, two cultures: does one nation have the right to call its own? It has been reported that South Korea will apply to the United Nations Educational, Social and Cultural Organization(UNESCO联合国教科文组织)to make the celebration its cultural heritage(文化遗产). If successful, people from other countries may see the Dragon Festival as a Korean creation.

As the birthplace of the yearly event more than 2,000 years ago, China is not happy with the situation. “It would be a shame if another country successfully made a traditional Chinese festival part of its own cultural heritage ahead of China,”said Zhou Heping, deputy culture minister. The Ministry of Culture is even thinking of making its own application to UNESCO, covering all traditional Chinese festivals, including the Dragon Boat event.

Over the years, the Dragon Boat Festival has spread throughout the world. In Japan and Viet Nam, as well as South Korea, the festival has mixed with and become part of local culture.

With this in mind, some experts say that it is meaningless to argue about which country the festival belongs to. “No one can deny that it came from China,”said Long Haiqing , an expert from Hunan Province. “But if all the countries involved can protect culture heritage together, they will all benefit.”

56. The underlined word “highlights”can be probably replaced by “     ”.

A. most exciting events     B. highest lights on the building

C. brightest lights at night    D. most famous festivals

57. It can be inferred that South Korea ______.

A. has proclaimed(宣布)the Dragon Boat Festival as a part of its cultural heritage

B. has the exactly same Dragon Boat Festival as China

C. has no idea that China has such a festival

D. is paying more attention to its cultural heritage than China

58. China is not happy with the situation because .

A. it created the festival

B. it is also making an application

C. South Korea has no right to call the festival its own

D. UNESCO may approve(批准)South Korea’s application

59. If South Korea’s application to UNESCO is successful, _____.

A. China will also make its own application to UNESCO

B. it will be meaningless to celebrate the Dragon Boat Festival

C. people from other parts of the world will think South Korea created the festival

D. the Dragon Boat Festival will become part of local culture

60. The author would probably support____ .

A. a move by South Korea to cancel its application

B. China getting UNESCO’s approval of the festival first

C. the opinion of Zhou Helping

D. China paying more attention to its cultural heritage