问题 选择题

叠放在一起的A、B两物体在水平力F的作用下,沿水平面以某一速度匀速运动,现突然将作用在B上的力F改为作用在A上,并保持大小和方向不变,如图所示,则关于A、B的运动状态可能为(    )

A.一起匀速运动    B.一起加速运动

C.A加速,B减速    D.A加速,B匀速

答案

AC

题目分析:据题意,拉力F作用在B上时做匀速运动,则有:;此时把F作用在A上,如果,则A物体做匀加速直线运动,A、B发生相对滑动,A物体作用在B物体上的摩擦力有:,则B物体做减速运动;如果,则A、B相对静止,且A、B整体有:,则A、B一起匀速运动。故选项A、C正确。

阅读理解

阅读理解

     People who have lost the ability to understand or use words due to brain damage are called aphasics(失语症患者). Such patients can be extremely good at something else. From the changing expressions on speakers' faces and the tones of their voices, they can tell lies from truths.

     Doctors studying the human brain have given a number of examples of this amazing power of aphasics. Some have even compared this power to that of a dog with an ability to find out the drugs hidden in the

baggage.

     Recently, scientists carried out tests to see if all that was said about aphasics was true. They studied a mixed group of people. Some were normal, others were aphasic. It was proved that the aphasics were far ahead of the normal people in recognizing false speeches-in most cases, the normal people were fooled by words, but the aphasics were not.

     Some years ago, Dr. Oliver Sacks wrote in his book about his experiences with aphasics. He

mentioned a particular case in a hospital. Some aphasics were watching the president giving a speech on

TV. Since the president had been an actor earlier, making a good speech was no problem for him. He was trying to put his feelings into every word of his speech.

     But his way of speaking had the opposite effect on the patients. They didn't seem to believe him.

Instead, they burst into laughter. The aphasics knew that the president did not mean a word of what he

was saying. He was lying!

     Many doctors see aphasics as people who are not completely normal because they lack the ability to

understand words. However, according to Dr. Sacks, they are more gifted than normal people. Normal

people may get carried away by words. Aphasics seem to understand human expressions better, though

they cannot understand words.

1. What is so surprising about aphasics?      

A. They can fool other people.

B. They can find out the hidden drugs.

C. They can understand language better.

D. They can tell whether people are lying.

2. How did the scientists study aphasics?    

A. By asking them to watch TV together.

B. By organizing them into acting groups.

C. By comparing them with normal people.

D. By giving them chances to speak on TV.

3. What do we learn from this text?      

A. What one says reflects how one feels.

B. Aphasics have richer feelings than others.

C. Normal people often tell lies in their speeches.

D. People poor at one thing can be good at another

填空题