图为蹦极运动的示意图．弹性绳的一端固定在O点，另一端和运动员_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题选择题

图为蹦极运动的示意图．弹性绳的一端固定在O点，另一端和运动员相连．运动员从O点自由下落，至B点弹性绳自然伸直，经过合力为零的C点到达最低点D，然后弹起．整个过程中忽略空气阻力．分析这一过程，下列表述正确的是（　　）

①经过B点时，运动员的速率最大

②经过C点时，运动员的速率最大

③从C点到D点，运动员的加速度增大

④从C点到D点，运动员的加速度不变．

A．①③

B．②③

C．①④

D．②④

答案

B点到C点，重力大于弹力，加速度方向向下，向下运动的过程中弹力增大，加速度减小，做加速度逐渐减小的加速运动，到达C点，加速度为零．从C点到D点，重力小于弹力，加速度方向向上，向下运动的过程中弹力增大，加速度增大，做加速度逐渐增大的减速运动．知C点的速率最大．故②③正确，①④错误．则B正确，A、C、D错误．

故选B．

选择题

—Could I use your computer?

— .

A．Yes, I am

B．I have no computer

C．Sorry, I’m using it

D．No, I can’t

完形填空

More Than I Had Dreamed Of
From the time I was seven, I had a dream of becoming a member of the Students Union. I always       my school leaders for taking responsibility for all of us. So I dreamed of being a leader.
Years flew by, and soon I was able to participate in the elections,       I would win. But the reality struck that I hadn’t had a chance. I wasn’t pretty. Girls across the school hardly knew me. I just did not have what it       to win a school election. I was       .
As I cried in my room that evening, I       took a deep breath and decided I wouldn’t stop dreaming. I decided that I would       elections again in my final year at school—and I would win.
I recognized that my       had a lot of things in their favor. What were the       that would work in my favor? I had good grades, and I was friendly and helpful. And my biggest         was the faith I had. I would not allow my       appearance to hold me back from putting my best foot forward. That evening, I       my election plans a whole year in advance.
I realized that girls would have to get to know me and recognize that I had the ability to       them. I loved making friends and I liked being helpful,       I decided that perhaps I could use these qualities to work to my advantage. In order to learn how to present a great election       , I also attended a course on effective public speaking.
The day after the election, when the principal(校长) announced I won the second highest number of votes, the students      . That joy on the faces of all my friends showed me that my victory was        theirs.
Suddenly, I realized that I had       much more than I had dreamed of. I had made many new friends and had helped people       the way. I had won the       and love of my school-mates and they knew me as somebody who would stand by them. I was able to put a smile on their faces and        their day.

C．calculating

B．immediately

C．impatiently

A．participate

C．schoolmates

D．competitors

B．accelerated

C．accomplished

A．appointment