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问题 填空题

将单摆挂在测力传感器的探头上，用测力探头和计算机组成的实验装置来测定单摆摆动过程中摆线受到的拉力（单摆摆角小于5°），计算机屏幕上得到如图a所示的图象．然后使单摆保持静止，得到如图b所示的图象．那么：

（1）此单摆的周期为______s．

（2）设摆球在最低点时重力势能EP=0，已测得当地重力加速度为g，单摆的周期用T表示，那么测得此单摆摆动时的机械能E的表达式是______．

A．E=

(F1-F3)gT2
8π2
    B．E=
(F1-F3)gT2
2π2
   C．E=
(F3-F2)gT2
4π2
    D．E=
(F3-F2)gT2
6π2
．

答案

（1）平衡位置处拉力最大，最大位移处拉力最小．从图a中看出单摆的周期为0.8s．

（2）单摆在最低点时F1-mg=m

v2
l
，mg=F3．根据周期公式摆长l=
gT2
4π2
，联立三个式子，得：EK=
1
2
mv2=
(F1-F3)gT2
8π2
．故A正确，B、C、D错误．

故选A．

单项选择题

When we think of leadership, we often think of strength and power. But what are these really, and how do they operate
Leadership today is not about forcing others to do things. If this is even possible, it is short term, and tends to backfire. If you order someone to do something against their will, they may do it because they feel they must, but the anger they feel will do more harm in the long term. They will also experience fear.
Fear causes the thinking brain to shut down, making the person unable to function at his or her best. If they associate you with this emotion of fear, they will become less functional around you, and you will have succeeded in not only shooting yourself in the foot, but possibly making a very good employee or partner unable to perform effectively. Fear has no place in leadership.
The way we influence people in a lasting way is by our own character, and our understanding and use of emotion. We can order someone to do something, which may be part of the workday; or we can employ them at the emotional level, so they become fully devoted to the projects and provide some of their own motivation. Today’s workplace is all about relationships as a human being as well as a worker. Everyone produces just a bit more for someone they like. Leaders understand the way things work. They know the paycheck is not the single most motivating factor in the work life of most people.
The true strength of leadership is an inner strength that comes from the confidence of emotional intelligence—knowing your own emotions, and how to handle them, and those of others. Developing your emotional intelligence is the single best thing you can do if you want to develop your relationships with people around you, which is the key to the leadership skills.

Which of the following is TRUE according to the passage

A. People tend to associate leadership with fear.
B. Working conditions affect people’s physical health.
C. Good relationship is the key to business success.
D. Smart people are more functional in the workplace.
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单项选择题

阶地是在地壳垂直运动的影响下，由河流下切侵蚀作用而形成，有几级阶地，就对应有几次地壳运动。下图示意某河流阶地的地形，其中等高距为20m。某地质考察队沿剖面线在①②③④⑤处分别钻孔至地下同一水平面，利用样本分析得知①⑤为同一岩层且岩层年龄较新，②④为同一岩层且岩层年龄较老。图示地区的地质地貌为（）

A、背斜山

B、向斜山

C、背斜谷

D、向斜谷
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