问题 问答题

如图所示剪刀的工作原理实际上就是杠杆的一种应用.

(1)请按图中的提示画出动力臂(标示为L1)和阻力臂(标示为L2).

(2)在 ______情况下,使用该剪刀比较省力,即该剪刀是省力杠杆.

答案

(1)过支点O分别作动力作用线和阻力作用的垂线段,即动力臂L1和阻力臂L2.如图所示

(2)因为省力杠杆是指动力臂大于阻力臂的杠杆,因此在动力臂大于阻力臂的情况下,使用剪刀比较省力,并且动力臂与阻力臂的比值越大时,使用起来会更加省力.

故答案为:动力臂大于阻力臂.

阅读理解

根据短文内容,完成下列各题。

     Do you have a goal for life? What's it? Do you want to become a writer, singer or just become a rich

person?

     A recent survey shows that in modern society, most people pick up practical goals, such as "earning

money to buy a house and a car", "to improve one's life quality", "finding a good job".

     Wang You worked in a small firm (商行) in Nanjing. The job was good and he didn't have to work

for extra hours. However, he felt the work was not exciting at all and the life was boring. So he gave up

his job and went to Beijing in February, 2007. When he arrived in Beijing, he set his new goal as finding

a good job.

     Nowadays more and more people want to live a better life. This fact shows that the society is making

progress and people's life goals have become more practical. One researcher says, "Everybody has his

/ her own life goal, which will be surely different from people to people. If one is poor, one's life goal will

be to earn more money; if one doesn't have a diploma, studying hard to get a diploma will become his life

goal; and if one doesn't have love, his life goal will be to look for it. But if one has no life goal, he will idle

away (虚度) his lifetime."

1. Did Wang You have to work for extra hours?

____________________________________________________

2. What will a poor man's life goal be according to this passage?

____________________________________________________

3. Where did Wang You work before he came to Beijing?

____________________________________________________

4. Why does the writer mention Wang You?

____________________________________________________

5. What's your life goal? How do you plan to achieve it?

____________________________________________________

判断题