问题 选择题

如图所示,表面光滑的曲面体上方有一固定的带电量为+Q 的点电荷,现有一带电量为+q的金属小球(可视为质点),在A点以初速度v0沿曲面射入,曲面体为绝缘体,小球与曲面相互绝缘,则(  )

A.小球从A点运动到B点过程中,速度逐渐减小

B.小球从A点到C点过程中,重力势能的增加量等于其动能的减少量

C.小球在C点时受到+Q的库仑力最大,所以对曲面的压力最大

D.小球在曲面上运动过程中,机械能始终守恒

答案

A、小球从A点运动到B点过程中,受重力、支持力和库仑力,库仑力向左下方,合力向左,加速度向左,故物体做减速运动,故A正确;

B、小球从A点到C点过程中,合力做负功,动能减小,重力势能和电势能都增加,总能量守恒,故重力势能的增加量小于其动能的减少量,故B错误;

C、小球在C点时受到+Q的库仑力最大,库仑力、重力和支持力的合力提供向心力,故在C点支持力不一定最大,故C错误;

D、小球在曲面上运动过程中,有重力和库仑力做功,动能、重力势能和电势能总量守恒,故机械能不守恒,故D错误;

故选A.

阅读理解

Doctor are known to be terrible pilots. They don't listen because they already know it all. I was lucky: I became a pilot in 1970, almost ten years before I graduated from medical school. I didn't realize then, but becoming a pilot makes me a better surgeon. I loved flying. As I flew bigger, faster planes, and in worse weather. I learned about crew resource management (机组资源管理), or CRM, a new idea to make flying safer. It means that crew members should listen and speak up for a good result, regardless of positions.

I first read about CRM in 1980. Not long after that, an attending doctor and I were flying in bad weather. The controller had us turn too late to get our landing ready. The attending doctor was flying; I was safety pilot He was so busy because of the bad turn, he had forgotten to put the landing gear (起落架) down. He was a better pilot - and my boss - so it felt unusual to speak up. But I had to: Our lives were in danger. I put aside my uneasiness and said, "We need to put the landing gear down now!" That was my first real lesson in the power of CRM, and I've used it in the operating room ever since.

CRM requires that the pilot/surgeon encourage others to speak up. It further requires that when opinions are from the opposite, the doctor doesn't overreact, which might prevent fellow doctors from voicing opinions again. So when I'm in the operating room, I ask for ideas and help from others. Sometimes they're not willing to speak up. But I hope that if I continue to encourage them , someday someone will keep me from “landing gear up”.

小题1:What dose the author say about doctors in general?

A.They like flying by themselves.

B.They are unwilling to take advice.

C.They pretend to be good pilots.

D.They are quick learners of CRM.小题2:The author deepened his understanding of the power of CRM when_______.

A.he saved the plane by speaking up

B.he was in charge of a flying task

C.his boss landed the plane too late

D.his boss operated on a patient小题3:In the last paragraph”landing gear up” probably means ______.

A.following flying requirements.

B.overreacting to different opinions.

C.listening to what fellow doctors say

D.making a mistake that may cost lives小题4:Which of the following can be the best title for the text?

A.CRM:A New Way to Make Flying Safe

B.Flying Makes Me a Better Doctor

C.The Making of a Good Pilot

D.A Pilot-Tumed Doctor

不定项选择