问题 不定项选择

如图所示,水平光滑的平行金属导轨左端接有电阻R,匀强磁场方向竖直向下,质量一定的金属棒OO'垂直于导轨放置,现使棒以一定的初速度v向右运动,当金属棒通过位置a、b时速度分别是va、vb,到位置c时刚好静止,导轨和金属棒的电阻不计,ab=bc,则下列关于金属棒在由a到b和由b到c的两个过程中的说法正确的是  

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A.两个过程金属棒的加速度相等  

B.两个过程通过电阻R的电荷量相等  

C.整个过程中金属棒做加速度减小的减速运动  

D.两个过程电阻R上产生的焦耳热相等

答案

BC

阅读理解

Mr. Evans lives in a city. He was a math teacher three years ago. He taught well and his students liked him. So he decided to work in the middle school all his life. But a terrible accident changed his fortune(命运).

One spring he took his class to visit a place of interest. The children saw a lot of interesting things and had a good time there. But on their way to school, their bus was hit by a truck because the young driver was drunk(醉的). Five students died and more than half of the children were injured in the accident. He didn’t know how it had happened and was very sad about it and after he came out of hospital, he left the school and became a policeman. He tried his best to stop the drivers from breaking the traffic regulations(违反交通规则). He worked hard and was strict with the drivers. So they were afraid of him.

One afternoon it was very hot. Mr. Evans was on duty. He was standing at the crossing and watching the traffic. Suddenly he saw a car rushing towards the crossing. It ran so fast that it almost hit a man on a bike. He stopped it at once and saw a girl in it.

"Show your license to me, madam," said Mr. Evans.

The girl handed her bag to him and said: "Please look for it in it. I can‘t see anything without glasses."

小题1:What was Mr. Evans’ job three years ago?

A.policeman

B.a math teacher

C.a guide

D.a drive小题2:Their bus was hit by a truck because___________.

A.the drunk driver broke the traffic rules

B.the bus driver broke the traffic rules

C.Mr. Evans broke the traffic rules

D.the children broke the traffic rules小题3:In the accident ___________.                 

A.more than half of the children died

B.five children were injured

C.more than half of those children were injured

D.Mr. Evans was injured小题4:The phrase “on duty” means “_____” in Chinese.               

A 在家里  B 在家  C 在值勤  D 在值日

小题5:From the story, we can infer that___________.

A.Mr. Evans would let girl drive away.

B.Mr. Evans would not let the girl drive away

C.Mr. Evans would look for the girl’s license in her bag

D.the girl would cry.

选择题