问题 选择题

两个小木块A和B用细线连在一起,中间夹着一轻质弹簧,放在光滑的水平台面上.现将细线烧断,木块A、B被弹簧弹出,最后落在水平地面上.落地点与平台边缘的水平距离分别为lA=1m,lB=2m,如图所示.则以下说法错误的是(  )

A.木块A、B离开弹簧时的速度大小之比vA:vB=1:2

B.木块A、B的质量之比mA:mB=2:1

C.木块A、B离开弹簧时的动能之比EkA:EkB=1:2

D.弹簧对木块A、B的冲量大小之比IA:IB=1:2

答案

A、木块被弹出离开桌面后做平抛运动,水平方向做运动运动,竖直方向做自由落体运动,因为下落的高度相等,所以运动的时间相等,

而lA=1m,lB=2m,所以vA:vB=1:2,故A正确;

B、根据动量守恒定律得:

mAvA=mBvB,所以mA:mB=2:1,故B正确;

C、根据动能的表达式EK=

1
2
mv2可知,EkA:EkB=1:2,故C正确;

D、根据动量定理得:IA:IB=mAvA:mBvB=1:1,故D错误.

本题选错误的

故选D

单项选择题 A1型题
阅读理解

阅读理解。

     Leadership is the art of getting someone to do something you want done because he wants to do it.

People naturally want to follow a good leader. After meeting with an effective leader it is not unusual to

feel uplifted(情绪高涨), inspired, and motivated to work towards a common goal.

     An effective leader makes others feel good about themselves, as well as the work they are doing. The

leader has a vision(幻想)of what he or she wants to achieve, and can communicate that vision to others in a way that makes people want to be part of it. One thing a good leader typically does is to communicate

the big picture, so that each employee can see how the particular role he or she plays makes a

contribution to the final result.

     Good leaders are positive and optimistic when they speak about the future. Their enthusiasm wins

them plenty of supporters who help make their vision a reality.

     Good leaders also understand that different people are motivated by different things. For employees

motivated by a need for achievement, a leader explains how the task offers an opportunity to take on a

challenge with an achievable goal. And employees are motivated by hearing how they will be part of a

team of people working together.

     Good leaders will introduce employees by name first, rather than job titles. They refer to employees as

team members, companions, or colleagues, never as "servants". Words have power, including the power

to make people feel whether or not they are important to the success of an organization.

     Good leaders believe that every team member matters and set up environments that make everyone

feel important. It is no wonder they can attract the support they need to help them achieve their goals.

1. What's the author's purpose of writing this passage? 

A. To tell us how to be a good leader at work.

B. To describe the proper relationship between leaders and employees. 

C. To inform us of how leaders and employees should communicate.

D. To show the optimism of a leader.

 2. What is the most important to be a good leader?

A. A good leader learns art very well.

B. A good leader can promote employees.

C. A good leader can satisfy all his or her employees.

D. A good leader can make employees happy and willing in their work.

3.What should a good leader do for an employee who wants to succeed at work? 

A. To promote the employee to a leadership role.

B. To draw a beautiful picture of the employee's future.

C. To encourage the employee to meet the challenges of his work.

D. To let the staff know the important role the employee plays.

4. What is Paragraph 6 mainly about?

A. The importance of making introductions by name.

B. A way of remembering others' names.

C. The key to the success of an organization.

D. How to create a harmonious relationship between leaders and employees.

5. We can infer from the passage that_________. 

A. a good leader is always good at creating comfortable working conditions

B. the support of employees is necessary for a leader to reach his goal

C. names are much easier to remember than job titles

D. the motivation of the employees all comes from the leader