搜题请搜索小程序“爱下问搜题”
问题 选择题

某些市提倡“绿色交通”体系，建立了一些彩色自行车道，推行“低碳生活”。到时候自行车会成为人们的重要交通工具，下列有关自行车的说法中正确的是[ ]

A．骑自行车匀速下坡时动能和机械能均不变

B．车把手是一个省力杠杆

C．自行车的座垫做得较宽大是为了减小对臀部的压力

D．骑自行车上坡前用力蹬车是为了增大惯性

答案

答案：B

计算题

电吹风是现代家庭的常用电器。如图甲所示是电吹风的电路原理图，R是电热丝，M是带动风扇转动的电动机，某电吹风的主要技术参数如图乙所示：

（1）当只闭合S1时，电吹风正常工作1min消耗的电能是多少J？

（2）当同时闭合S1、S2时，电吹风正常工作，通过R的电流为多大？

（3）当电吹风正常工作并且吹热风时，1min内电流通过R产生的热量是多少J？

查看答案
填空题

Part 3


Questions 19-25


·Read the following passage and answer questions 19-25.
·For questions 19-25, choose the correct answer from A, B, C and D.
·Markyour answers on the Answer Sheet.
It is natural for young people to be critical of their parents at times and to blame them for the most of the misunderstandings between them. They have always complained, more or less justly, that their parents are out of touch with modern way; that they are possessive and dominant; that they don’t trust their children to deal with the crisis; that they talk too much about certain problems — and that they have no sense of humor, at least in parent-child relationships.
I think it is true that parent often underestimate their teenage children and also forget how they themselves felt when young.
Young people often irritate their parent with their choices in clothes and hairstyles, in entertainers and music. This is not their motive. They feel cut off from adult world into which they have not yet been accepted. So they create a culture of society of their own. Then, it turns out that their music and entertainers or vocabulary or clothes or hairstyles irritate their parents. This gives them additional enjoyment. They feel they are superior, at least in a small way, and they are leaders in style and taste.
Sometimes you are resistant, and proud because you don’t want your parents to approve what you do. If they did approve, it looks as if you are betraying your own age group. But in that cases, you are assuming that you are an underdog: you can’t win but at least you can keep your honor. There is a passive way of looking at things. It is natural enough after long years of childhood, when you are completely under your patents’ control. But it ignores the face that you are now beginning to be responsible for yourself.
If you plan to control your life, cooperation can be part of that plan. You can charm others, especially your parents, into doing things the way you want. You can impress your parents with your sense of responsibility and initiative, so that they will give you the authority to do what you want to do.

Teenagers tend to have strange clothes and hairstyles because they ______.

A．have a p desire to be leaders in style and taste

B．have no other way to enjoy themselves better

C．want to irritate their parents

D．want to show their existence by creating a culture of their own
查看答案