题干

小明用50N的水平力把重20N的木块压在竖直墙面上,使木块静止不动,此时木块受到的摩擦力大小是____ N,若减小水平压力,木块仍静止,则木块受到的摩擦力____.若木块原来处于下滑过程中,减小压力,木块受到的摩擦力将____.(后两空填“变大”“不变”,“变小”).
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答案(点此获取答案解析)

20,不变,变小

同类题4

阅读下面短文,然后按要求写一篇150词左右的英语短文。

    “When should I begin to acquire good habits?”a young boy asked his teacher.

    “How old are you?” asked the teacher.

    “Eight years old, sir.”answered the boy.

    “Then you have just lost eight years,”the teacher replied.

    There is no doubt that habits are formed at a very early age. When one is young, it is easy to acquire good habits.

    Good habits are practices that help us in our daily life. The habit of brushing one's teeth in the morning, for instance, keeps one's teeth clean and prevents a bad smell which is unpleasant to others. Bad habits such as sticking one's tongue out, biting one's fingernails and picking one's nose, are undesirable ways of behaving in front of others. If we want people to enjoy being with us, we should try to develop habits that are pleasant.

    It is said, “We sow an act; we reap a habit. We sow a habit and we reap a character.” The habits we formed at an early age shape our character. Habits are like tributaries(支流) which flow into a river. The river is made up of all its tributaries; a person's character is made up of all the habits that he or she has acquired over the years.

【写作内容】

1)以约30个词概括本文内容;

2)以约120个词谈谈你对好习惯养成的看法,并包括以下要点:

①你认为好习惯重要吗,为什么?

②你身上有哪些好习惯,它们对你的学习或生活有什么影响?

③怎样才能养成良好的习惯?

【写作要求】

1)作文中可以使用亲身经历或虚构的故事,也可以参照阅读材料的内容,但不得直接引用原文的句子。

2)作文中不得出现真实姓名和学校名称。