问题 计算题

(10分)从粒子源射出的带电粒子的质量为m、电荷量为q,它以速度v0经过电势差为U的带窄缝的平行板电极S1S2间的电场,并从O点沿Ox方向进入磁感应强度为B、方向垂直纸面向外的有界匀强磁场,Ox垂直平行板电极S2,当粒子从P点离开磁场时,其速度方向与Ox方向的夹角θ=60°,如图8-2-20所示,整个装置处于真空中.

(1)求粒子在磁场中沿圆弧运动的轨道半径R

(2)求粒子在磁场中运动所用的时间t.

答案

(1) (2)

题目分析:(1)粒子进入平行板中的匀强电场,则电场力对其加速,利用动能定理则:

所以出电场的末速度为

根据洛伦兹力提供向心力有,即,带入则

(2)

根据粒子在磁场中的运动轨迹可知,在磁场中轨迹的圆心角为60°。即

点评:此类题型属于比较常规型的带电粒子在电场或者磁场中的运动问题。根据动能定理可以求出在电场中加速后的末速度。通过左手定则定圆心,画轨迹,从而根据几何知识判断出半径。

阅读理解

Successful people in international business understand the cultures of other countries and learn to change their practices in different cultures. They understand the importance of avoiding business decisions based on misconceptions—mistaken ideas. 

One cause of misconceptions is ethnocentrism, the belief that one’s own culture’s way of doing things is better than the way of other cultures. It’s ethnocentrism that leads to failure in international business. To avoid ethnocentrism, it’s necessary to study the different elements(组成部分)of culture: language, values and attitudes, and customs and manners. 

Language

A. knowledge of the local language can help international business people in four ways. First, people can communicate directly. Second, people are usually more open in their communication with someone who speaks their language. Third, an understanding of the language allows people to infer meanings that are not said directly. Finally, knowing the language helps people to understand the culture better.  

Values are people’s basic beliefs about the difference between right and wrong, good and bad . An attitude is a way of thinking or acting. Values and attitudes influence international business. For example, many people in the United States believe that chocolate from Switzerland is better than chocolate from other countries, and they buy a lot of it. 

Customs and manners

Customs are common social practices. Manners are ways of acting that the society believes are polite. For example, in the United States,  it is the custom to have salad (色拉) before the main course at dinner, not after. It’s not acceptable to talk with food in mouth at table. Failure to understand the customs and manners of other countries will bring difficulty selling their products. Orange juice as a breakfast drink of an American company in France doesn’t sell well because the French don’t usually drink juice with breakfast. 

小题1:A. knowledge of the local language allows international business people _________. 

A. to be more open with their customers

B. to communicate without outside help

C. to express their thoughts indirectly

D. to have a better idea of their own culture

小题2:The act of many people buying chocolate of Switzerland shows the role of ________. 

A.manners

B.values

C.attitudes

D.customs小题3:What would be the best title for the text?                    

A.Misconceptions in Business

B.Basic Beliefs in Business

C.International Business Culture

D.Successful International Business小题4:The author’s purpose of writing this article is to tell people ___________       

A.how to take a right attitude in business

B.how to avoid misunderstandings in business

C.how to use a local language in business

D.how to act politely and properly in business

问答题 简答题