问题 多项选择题

一个做变速直线运动的物体,加速度逐渐减小到零,那么该物体的运动情况可能是()

A.速度不断增大,到加速度为零时,速度达到最大,而后做匀速直线运动

B.速度不断增大,到加速度减为零时,物体停止运动

C.速度不断减小到零,然后又相反方向做加速运动,而后物体做匀速直线运动

D.速度不断减小,到加速度为零时速度减到最小,而后物体做匀速直线运动

答案

参考答案:A, C, D

解析:直线运动的物体,题目只是告诉加速度逐渐减小到0,只是大小变化,方向没有变化。如果速度与加速度同向是加速运动,速度变大,速度与加速度反向是减速运动,速度减小。如果开始时速度与加速度同向,那么速度逐渐增大,加速度大小变小只会使速度增加的慢了,但速度仍是增大的,当加速度减小为0时,速度最大此后开始匀速直线运动,A正确。如果开始时速度与加速度反向,那么速度逐渐减小,如果在加速度减小的过程中,速度一直没有减小到0,那么当加速度等于0时速度最小,此后为匀速直线运动,D对,但是也有可能在加速度减小到0之前速度先减小到0,那么速度就会反向,就会由与加速度反向变为与加速度同向而成为加速运动速度增大,当加速度等于0时,速度不再增大而变为匀速直线运动,C对

阅读理解

Luo Gaoqi hopes to join the increasing number of Chinese students in the United States because he wants the experience of studying in a foreign land as it will help his future job at home. “I want to try Western education because people there think differently,” said the 21-year-old who is in his final year of undergraduate studies. “I also hope to meet friends from different cultures. The social connections may help in the future.”

The latest report from the US-based institute of International Education said China, for the first time, has become the top country of origin for international students in the United States.

For Yang Fan, a journalism student, said studying in the United States is a way to escape the competition for places in China’s top universities.

“Due to limited education resources, only about 60 percent of high school graduates in China enter college, and a much lower rate enters the top-level ones. “A foreign degree will definitely help when I seek a job in China,” Yang said.

Both Yang’s and Luo’s parents are supportive of them studying abroad. Neither of them is thinking of settling down in the United States after graduation.

“It is not realistic to do so. As a journalism student, there would be no advantage for me to work in the United States,” Yang said. “But in China, with a US degree and good English, I may stand out against other students who have only studied in China.”

China still needs to improve its environment for scientists and high-level talents, said Xiao Mingzheng, director of the Center for Human Resource Development and Management Research of Peking University, adding that, in particular, the country needs to improve its policies relating to research environments.

In June, the Chinese government published a plan concerning talent development for the next 10 years. In it, it has improved policies and increased budgets to attract talented students back home.

小题1:Why does Luo Gaoqi wants to study in a foreign land according to his words?

A.Because the people there are more intelligent.

B.Because the foreign countries are more developed.

C.Because he can make more friends there.

D.Because the culture there is different from that in China.小题2:What do Guo Gaoqi and Yang Fan have in common?

A.Their major is the same, which is journalism.

B.Both of them want to go back to China after graduation.

C.Their parents are against their decision.

D.They are forced to study in a foreign land by their parents.小题3:From the passage, we can infer that _______.

A.scientists and high-level talents need a better environment in China

B.the students abroad are unwilling to go back to China

C.China doesn’t need those people to come back to our country at all

D.we all need to go abroad to study and then serve our own country

判断题