问题 问答题

人在平地上行走时,如果让脚轮流向后蹬地,人就一直向前走,做直线运动。结合自己的情况,分析人若要向右转弯,脚需如何蹬地?

答案

人在向右转弯时做的是曲线运动,因而应该从物体做曲线运动的条件人手,通过分析运动轨迹来确定脚蹬地的方向。由物体曲线运动的条件和动力学知识可知,人向右转时应受到向右的作用力,而这一力是由地面作用于人的静摩擦力提供的。由牛顿第三定律可知,人应该用左脚向左后方蹬地,人才能够向右转。

阅读理解

阅读理解。根据短文完成下边的对话A-reporter B-me。

                                                                           My school life

     My home is far from our school. So I live in school from Monday to Friday. In school, there are many

  friends. We can play and study together. It's fun. This term, school begins at 8:00. We have more (更多

 的) time to sleep. Everyone is happy. I usually eat bread for breakfast at half past seven. After lunch and

  supper, I usually go for walks (去散步) with my classmates for about fifteen minutes (分钟).

     We have twelve subjects in school. I like English best! Our English teacher teaches us a lot. And she is

 lovely and fairly. We all like her. We have much fun in English classes.

     In school, I hate washing clothes (洗衣服). It's tired and boring. We don't have too much homework in

  school. Sometimes, I go to the library to read books. It's good for me. Now I am in grade 2, I must work

  hard. I think I can be a good student. What about you? Let's study hard together!

A: Do you go to school every day?

B: No. I live __1__ our school. So I live in school on weekdays.

A: Do you like to live in school?

B: Yes. Because I can __2__ with my friends.

A: When do you begin school?

B: __3__ .

A: Well, you can have more time to sleep.

B: Yes, and Everyone is happy.

A: What do you usually do after lunch?

B: __4__ .

A: It's good for your health (健康). Can you tell me what your favorite subject is?

B: __5__ .

A: Thank you!

单项选择题