如图所示,足够长的水平桌面上静止一质量为0.2kg的木块,用弹簧秤沿水平方向拉木

题型:填空题

问题:

如图所示,足够长的水平桌面上静止一质量为0.2kg的木块,用弹簧秤沿水平方向拉木块。当弹簧秤示数是0.3N时,木块未被拉动,这时木块受到的摩擦力是________(选填“滑动”、“静”或“滚动”)摩擦力,大小_______N,方向___________;当弹簧秤示数是0.4N时,木块正好作匀速运动;当弹簧秤示数是0.6N时,木块所受的摩擦力大小为____________N,木块的运动状态_______(选填“改变”或“不改变”)。

考点:摩擦力的种类
题型:填空题

    Nathan Sawaya's childhood was a lot of fun. He drew cartoons, wrote stories, and played with plastic toy bricks (积木). His grandparents bought his first set of toy bricks when he was five years old and he's been building with toy bricks ever since. He even took his building bricks to college with him! Instead of books and a computer, he had a model of Greenwich Village made of bricks on his desk. 

    Nathan started as a lawyer but gave up His highly-paid (高薪的) job to become an artist that uses toys in his art. He uses toy bricks to build everything from the Statue of Liberty(自由女神像) to Superman! He has more than 1.5 million colored bricks in his working room in New York which he uses to make pieces of art. He started by building small models but then decided to do something big and created a self-portrait (自画像). It took him two days just to build the eyes.

     Nathan's work has appeared in museums around the world. Children love his art because it is made out of the same toys that they play with at home and adults love his work because it is fascinating. Since it began in2007, Nathan's exhibition "The Art of the Brick" has been very popular with museum visitors everywhere.     "I'm proud that I took a dream I had as a child, to become an artist, and I have actually made a job out of it," says Nathan. "To do what you love in life is the most important thing." 

1. What did Nathan put on his desk at college? 

A. The Statue of Liberty.    B. Superman.    C. His serf-portrait.    D. A Greenwich Village modal. 

2. Why did Nathan give up his job as a lawyer? 

A. Because he made little money out of a lawyer.

B. Because he wanted to make toys for the children.

C. Because he decided to become an artist of toy bricks.

D. Because he was going to work in the museum instead.

3. What does the underlined word "it" in Paragraph 3 refer to? 

A. Nathan's work.                 B. Nathan's exhibition.        C. Nathan's art.      D. Nathan's self-portrait

4. What would be the best title for the passage?

A. The Brick Artist                    B. The Brick Exhibition

C. Toy Bricks for Adults           D. The Artist's Childhood

题型:填空题

If you feel tired, you  may stop _____.  [ ]

A. have a rest

B. to have a rest

C. having a rest

D. has a rest

题型:填空题

在380/220伏接地系统中,电气设备均采用()保护

A.接地

B.接零

C.零序

题型:填空题

以下哪些不是属于供应商因在生产能力方面出现的问题______。

A.生产交货时间计算错误
B.临时急单插入
C.小批量订单需合起来生产
D.需调度的材料、零配件采购延迟,生产量掌握不正确
E.不合格品产生较多

题型:填空题

为了看清零件的内部(),在零件图中就出现了将零件切开的剖视图。

A.尺寸

B.公差要求

C.结构

D.形状

E.组成

F.构成

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